Category Archives: Space

Water, weather, new worlds: Cassini mission revealed Saturn’s secrets

Dan Reisenfeld, The University of Montana

Cassini is the most sophisticated space probe ever built. Launched in 1997 as a joint NASA/European Space Agency mission, it took seven years to journey to Saturn. It’s been orbiting the sixth planet from the sun ever since, sending back data of immense scientific value and images of magnificent beauty.

Cassini now begins one last campaign. Dubbed the Grand Finale, it will end on Sept. 15, 2017 with the probe plunging into Saturn’s atmosphere, where it will burn up. Although Saturn was visited by three spacecraft in the 1970s and 1980s, my fellow scientists and I couldn’t have imagined what the Cassini space probe would discover during its sojourn at the ringed planet when it launched 20 years ago.

A huge storm churning across the face of Saturn. At the time this image was taken, 12 weeks after the storm began, it had completely wrapped around the planet.
NASA/JPL-Caltech/SSI, CC BY

A planet of dynamic change

Massive storms periodically appear in Saturn’s cloud tops, known as Great White Spots, observable by Earthbound telescopes. Cassini has a front-row seat to these events. We have discovered that just like Earth’s thunderstorms, these storms contain lightning and hail.

Cassini has been orbiting Saturn long enough to observe seasonal changes that cause variations in its weather patterns, not unlike the seasons on Earth. Periodic storms often appear in late summer in Saturn’s northern hemisphere.

In 2010, during northern springtime, an unusually early and intense storm appeared in Saturn’s cloud tops. It was a storm of such immensity that it encircled the entire planet and lasted for almost a year. It was not until the storm ate its own tail that it eventually sputtered and faded. Studying storms such as this and comparing them to similar events on other planets (think Jupiter’s Great Red Spot) help scientists better understand weather patterns throughout the solar system, even here on Earth.

Having made hundreds of orbits around Saturn, Cassini was also able to deeply investigate other features only glimpsed from Earth or earlier probes. Close encounters with Saturn’s largest moon, Titan, have allowed navigators to use the moon’s gravity to reorient the probe’s orbit so that it could swing over Saturn’s poles. Because of Saturn’s strong magnetic field, the poles are home to beautiful Aurorae, just like those of Earth and Jupiter.

Saturn’s six-sided vortex at Saturn’s north pole known as ‘the hexagon.’ This is a superposition of images taken with different filters, with different wavelengths of light assigned colors.
NASA/JPL-Caltech/SSI/Hampton University, CC BY

Cassini has also confirmed the existence of a bizarre hexagon-shaped polar vortex originally glimpsed by the Voyager mission in 1981. The vortex, a mass of whirling gas much like a hurricane, is larger than the Earth and has top wind speeds of 220 mph.

Home to dozens of diverse worlds

Cassini discovered that Saturn has 45 more moons than the 17 previously known – placing the total now at 62.

The largest, Titan, is bigger than the planet Mercury. It possesses a dense nitrogen-rich atmosphere with a surface pressure one and a half times that of Earth’s. Cassini was able to probe beneath this moon’s cloud cover, discovering rivers flowing into lakes and seas and being replenished by rain. But in this case, the liquid is not water, but rather liquid methane and ethane.

False-color image of Ligeia Mare, the second largest known body of liquid on Saturn’s moon Titan. It’s filled with liquid hydrocarbons.
NASA/JPL-Caltech/ASI/Cornell, CC BY

That’s not to say that water is not abundant there – but it’s so cold on Titan (with a surface temperature of -180℃) that water behaves like rock and sand. Although it has all the ingredients for life, Titan is essentially a “frozen Earth,” trapped at that moment in time before life could form.

The sixth-largest moon of Saturn, Enceladus, is an icy world about 300 miles in diameter. And for me, it’s the site of the Mission’s most spectacular finding.

The discovery started humbly, with a curious blip in magnetic field readings during the first flyby of Enceladus in 2004. As Cassini passed over the moon’s southern hemisphere, it detected strange fluctuations in Saturn’s magnetic field. From this, the Cassini magnetometer team inferred that Enceladus must be a source of ionized gas.

Intrigued, they instructed the Cassini navigators to make an even closer flyby in 2005. To our amazement, the two instruments designed to determine the composition of the gas that the spacecraft flies through, the Cassini Plasma Spectrometer (CAPS) and the Ion and Neutral Mass Spectrometer (INMS), determined that Cassini was unexpectedly passing through a cloud of ionized water. Emanating from cracks in the ice at Enceladus’ south pole, these water plumes gush into space at speeds up to 800 mph.

I am on the team that made the positive identification of water, and I have to say it was the most thrilling moment in my professional career. As far as Saturn’s moons were concerned, everyone thought all of the action would be at Titan. No one expected small, unassuming Enceladus to harbor any surprises.

Geologic activity happening in real time is quite rare in the solar system. Before Enceladus, the only known active world beyond Earth was Jupiter’s moon Io, which possesses erupting volcanoes. To find something akin to Old Faithful on a moon of Saturn was practically unimaginable. The fact that it all started with someone noticing an odd reading in the magnetic field data is a wonderful example of the serendipitous nature of discovery.

The geyser basin at the south pole of Enceladus, with its water plumes illuminated by scattered sunlight.
NASA/JPL-Caltech/Space Science Institute, CC BY

The story of Enceladus only becomes more extraordinary. In 2009, the plumes were directly imaged for the first time. We now know that water from Enceladus comprises the largest component of Saturn’s magnetosphere (the area of space controlled by Saturn’s magnetic field), and the plumes are responsible for the very existence of Saturn’s vast E-ring, the second outermost ring of the planet.

More amazingly, we now know that beneath the crust of Enceladus is a global ocean of liquid saltwater and organic molecules, all being heated by hydrothermal vents on the seafloor. Detailed analysis of the plumes show they contain hydrocarbons. All this points to the possibility that Enceladus is an ocean world harboring life, right here in our solar system.

NASA at Saturn: Cassini’s Grand Finale.

When Cassini plunges into the cloud tops of Saturn later this year, it will mark the end of one of the most successful missions of discovery ever launched by humanity.

Scientists are now considering targeted missions to Titan, Enceladus or possibly both. One of the most valuable lessons one can take from Cassini is the need to continue exploring. As much as we learned from the first spacecraft to reach Saturn, nothing prepared us for what we would find with Cassini. Who knows what we will find next?

Dan Reisenfeld, Professor of Physics & Astronomy, The University of Montana

Our discovery of a minor planet beyond Neptune shows there might not be a ‘Planet Nine’ after all

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Ever since enthusiasm started growing over the possibility that there could be a ninth major planet orbiting the sun beyond Neptune, astronomers have been busy hunting it. One group is investigating four new moving objects found by members of the public to see if they are potential new solar system discoveries. As exciting as this is, researchers are also making discoveries that question the entire prospect of a ninth planet.

One such finding is our discovery of a minor planet in the outer solar system: 2013 SY99. This small, icy world has an orbit so distant that it takes 20,000 years for one long, looping passage. We found SY99 with the Canada-France-Hawaii Telescope as part of the Outer Solar System Origins Survey. SY99’s great distance means it travels very slowly across the sky. Our measurements of its motion show that its orbit is a very stretched ellipse, with the closest approach to the sun at 50 times that between the Earth and the sun (a distance of 50 “astronomical units”).

The new minor planet loops even further out than previously discovered dwarf planets such as Sedna and 2013 VP113. The long axis of its orbital ellipse is 730 astronomical units. Our observations with other telescopes show that SY99 is a small, reddish world, some 250 kilometres in diameter, or about the size of Wales in the UK.

SY99 is one of only seven known small icy worlds that orbit beyond Neptune at remarkable distances. How these “extreme trans-Neptunian objects” were placed on their orbits is uncertain: their distant paths are isolated in space. Their closest approach to the sun is so far beyond Neptune that they are thought to be “detached” from the strong gravitational influence of the giant planets in our solar system. But at their furthest points, they are still too close to be nudged around by the slow tides of the galaxy itself.

Planet Nine could explain why the few known extreme trans-Neptunian objects seem to be clustered together in space. The diagram was created using WorldWide Telescope.
Caltech/R. Hurt (IPAC)

It’s been suggested that the extreme trans-Neptunian objects could be clustered in space by the gravitational influence of a “Planet Nine” that orbits much further out than Neptune. This planet’s gravity could lift out and detach their orbits – constantly changing their tilt. But this planet is far from proven.

In fact, its existence is based on the orbits of only six objects, which are very faint and hard to discover even with large telescopes. They are therefore prone to odd biases. It’s a bit like looking down into the deep ocean at a school of fish. The fish swimming near the surface are clearly visible. But the ones even only a meter down are fainter and murky, and take quite a lot of peering to be certain. The great bulk of the school, in the depths, is completely invisible. But the fish at the surface and their behaviour betray the existence of a whole school.

The biases mean SY99’s discovery can’t prove or disprove the existence of a Planet Nine. However, computer models do show that a Planet Nine would be an unfriendly neighbour to tiny worlds like SY99: its gravitational influence would starkly change its orbit – throwing it from the solar system entirely, or poking it into an orbit so highly inclined and distant that we wouldn’t be able to see it. SY99 would have to be one of an utterly vast throng of small worlds, continuously being sucked in and cast out by the planet.

The alternative explanation

But it turns out that there are other explanations. Our study based on computer modelling, accepted for publication in the Astronomical Journal, hint at the influence of an idea from everyday physics called diffusion. This is a very common type of behaviour in the natural world. Diffusion typically explains the random movement of a substance from a region of higher concentration to one of lower concentration – such as the way perfume drifts across a room.

We showed that a related form of diffusion can cause the orbits of minor planets to change from an ellipse that is initially only 730 astronomical units on its long axis to one that is as big as 2,000 astronomical units or bigger – and change it back again. In this process, the size of each orbit would vary by a random amount.
When SY99 comes to its closest approach every 20,000 years, Neptune will often be in a different part of its orbit on the opposite side of the solar system. But at encounters where both SY99 and Neptune are close, Neptune’s gravity will subtly nudge SY99, minutely changing its velocity. As SY99 travels out away from the sun, the shape of its next orbit will be different.

The long axis of SY99’s ellipse will alter, becoming either larger or smaller, in what physicists call a “random walk”. The orbit change takes place on truly astronomical time scales. It diffuses over the space of tens of millions of years. The long axis of SY99’s ellipse would change by hundreds of astronomical units over the 4.5 billion-year history of the solar system.

Several other extreme trans-Neptunian objects with smaller orbits also show diffusion, on a smaller scale. Where one goes, more can follow. It’s entirely plausible that the gradual effects of diffusion act on the tens of millions of tiny worlds orbiting in the near fringe of the Oort cloud (a shell of icy objects at the edge of the solar system). This gentle influence would slowly lead some of them to randomly shift their orbits closer to us, where we see them as extreme trans-Neptunian objects.

However, diffusion won’t explain the distant orbit of Sedna, which has its closest point too far out from Neptune for it to change its orbit’s shape. Perhaps Sedna gained its orbit from a passing star, aeons ago. But diffusion could certainly be bringing in extreme trans-Neptunian objects from the inner Oort cloud – without the need for a Planet Nine. To find out for sure, we’ll need to make more discoveries in this most distant region using our largest telescopes.

Michele Bannister, Research Fellow, planetary astronomy, Queen’s University Belfast

This article was originally published on The Conversation. Read the original article.

NASA: Saturn moon Enceladus is able to host life – it’s time for a new mission

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David Rothery, The Open University

Ever since studies started suggesting that chemical reactions between water and rock on Saturn’s moon Enceladus could provide enough energy in the water to feed microbial life, scientists have been searching for proof that the right sort of reactions really do occur.

And during its last dive through the icy plumes that Enceladus erupts into space in October 2015, the Cassini spacecraft has finally managed to find it – in the form of molecular hydrogen. The finding, published in Science, means the moon can now be considered highly likely to be suitable to host microbial life. In fact, the results should undermine the last strong objection from those who argue it could not.

Enceladus is a small (502km in diameter) moon with an icy surface, a rocky interior and an ocean of liquid water sandwiched between the two. Cassini discovered back in 2005 that Enceladus is venting water into space, in the form of plumes of ice crystals escaping from cracks in the surface. For a decade, Enceladus was the only icy moon where this was known to happen, but plumes have recently been found on Europa, too, a larger icy moon of Jupiter.

Cassini’s discovery led to it being re-tasked to fly through Enceladus’s plumes. There, in addition to water, it was able to identify traces of methane, ammonia, carbon monoxide, carbon dioxide, simple organic molecules and salts.

Cutaway view inside Enceladus, showing where hot water and rock interact below the ice.
NASA/JPL

Eventually, in March 2015, it detected microscopic particles of silica. By then, the composition of the plumes showed almost every sign that ocean water had reacted chemically with heated rock – altering the minerals of the rocky silicate seabed while the water became rich in chemicals.

Presumably, the ocean water is drawn into the rock, becomes heated, reacts chemically, and escapes back up to the ocean via “hydrothermal vents”. These exist on the floor of the Earth’s oceans, too, where the chemically charged water supports a rich ecology of microbes and other, more complex, life forms – requiring no sunlight.

The only missing evidence of water-rock chemical reactions in Enceladus was molecules of hydrogen, which should be released as a byproduct of the water-rock reactions. Searching for hydrogen was a key goal of Cassini’s final and closest dive through the plumes.

The new study unveils how hydrogen was detected during the frantic half-minute when Cassini was about 120km above the surface of Enceladus, whizzing through a plume at 8.5km per second. This was achieved by operating the mass spectrometer (an instrument which knocks electrons off chemical substances and sorts them based on their mass-to-charge ratio) in a special mode. It admitted plume material directly into the instrument’s detection chamber to avoid the possibility of hydrogen being generated by plume-water reacting with the metallic components of the instrument itself.

The astrobiology

Hydrogen is of immense significance, because its presence along with hot water and rock would enable simple microbes to make a living. When dissolved carbon dioxide reacts with dissolved hydrogen, it produces methane and water. This chemical reaction releases energy that organisms can use to drive their metabolism. There are many kinds of “methanogenic” organisms at deep sea hydrothermal vents on Earth that do this. Now that we know Enceladus has all the necessary ingredients for this to happen, we are lacking only the proof of life itself.

For that we will need a purpose-built mission, such as the Enceladus Life Finder (ELF). This would collect and analyse any complex organic molecules in the plumes. It is hard to imagine a more important goal for solar system exploration than establishing whether a habitable environment, such as the warm bottom of Enceladus’s ocean, actually does host life.

Enceladus’s south polar plumes, as seen by Cassini November 30 2010.
NASA/JPL-Caltech/Space Science Institute

Enceladus is a long way from Earth. If we were able to prove that it hosts life, it would be highly likely that such life had originated there, independently of life on Earth. That would be a crucial discovery. It would provide evidence to suggest that our galaxy is teeming with life, because if life began independently on two different bodies in our solar system, then surely it also got going on many of the potentially habitable planets that we are now finding around other stars.

Enceladus is a tiny world, and the amount of available energy and nutrients is small. Few scientists therefore expect it to host an ecosystem consisting of more than simple microbes. The much larger Europa, if it has life too, is a better prospect.

How Cassini will end, on September 15, 2017.
NASA/Jet Propulsion Laboratory-Caltech

However, to protect Enceladus from the slightest risk of contamination by any terrestrial microbes that accidentally hitched a ride on Cassini, the craft will not be allowed to become a derelict object that might eventually crash onto its surface. Instead, the mission is facing its “grand finale”, a series of 22 orbits in which it will pass spectacularly between Saturn and its innermost ring. This will end with Cassini burning up in Saturn’s atmosphere.

David Rothery, Professor of Planetary Geosciences, The Open University

This article was originally published on The Conversation. Read the original article.

Watching the planet breathe: Studying Earth’s carbon cycle from space

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Berrien Moore III, University of Oklahoma and Sean Crowell, University of Oklahoma

Carbon is a building block of life on our planet. It is stored in reservoirs on Earth – in rocks, plants and soil – in the oceans, and in the atmosphere. And it cycles constantly between these reservoirs.

Understanding the carbon cycle is crucially important for many reasons. It provides us with energy, stored as fossil fuel. Carbon gases in the atmosphere help regulate Earth’s temperature and are essential to the growth of plants. Carbon passing from the atmosphere to the ocean supports photosynthesis of marine phytoplankton and the development of reefs. These processes and myriad others are all interwoven with Earth’s climate, but the manner in which the processes respond to variability and change in climate is not well-quantified.

Our research group at the University of Oklahoma is leading NASA’s latest Earth Venture Mission, the Geostationary Carbon Observatory, or GeoCarb. This mission will place an advanced payload on a satellite to study the Earth from more than 22,000 miles above the Earth’s equator. Observing changes in concentrations of three key carbon gases – carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO) – from day to day and year to year will help us to make a major leap forward in understanding natural and human changes in the carbon cycle.

GeoCarb is also an innovative collaboration between NASA, a public university, a commercial technology development firm (Lockheed Martin Advanced Technology Center) and a commercial communications launch and hosting firm (SES). Our “hosted payload” approach will place a scientific observatory on a commercial communications satellite, paving the way for future low-cost, commercially enabled Earth observations.

Observing the carbon cycle

The famous “Keeling curve,” which tracks CO2 concentrations in Earth’s atmosphere, is based on daily measurements at Mauna Loa Observatory on Hawaii. It shows that global CO2 levels are rising over time, but also change seasonally due to biological processes. CO2 decreases during the Northern Hemisphere’s spring and summer months, as plants grow and take CO2 out of the air. It rises again in fall and winter when plants go relatively dormant and ecosystems “exhale” CO2.

Recorded starting in 1958 by the late geochemist Charles David Keeling, the Keeling curve measures atmospheric carbon dioxide concentrations.
Scripps Institution of Oceanography

A closer look shows that every year’s cycle is slightly different. In some years the biosphere takes more CO2 out of the atmosphere; in others it releases more to the atmosphere. We want to know more about what causes the year-to-year differences because that contains clues on how the carbon cycle works.

For example, during the El Niño of 1997-1998, a sharp rise in CO2 was largely driven by fires in Indonesia. The most recent El Niño in 2015-2016 also led to a rise in CO2, but the cause was probably a complex mixture of effects across the tropics – including reduced photosynthesis in Amazonia, temperature-driven soil release of CO2 in Africa and fires in tropical Asia.

These two examples of year-to-year variability in the carbon cycle, both globally and regionally, reflect what we now believe – namely, that variability is largely driven by terrestrial ecosystems. The ability to probe the climate-carbon interaction will require a much more quantitative understanding of the causes of this variability at the process level of various ecosystems.

Why study terrestrial emissions from space?

GeoCarb will be launched into geostationary orbit at roughly 85 degrees west longitude, where it will rotate in tandem with the Earth. From this vantage point, the major urban and industrial regions in the Americas from Saskatoon to Punta Arenas will be in view, as will the large agricultural areas and the expansive South American tropical forests and wetlands. Measurements of carbon dioxide, methane and carbon monoxide once or twice daily over much of the terrestrial Americas will help resolve flux variability for CO2 and CH4.

GeoCarb also will measure solar induced fluorescence (SIF) – plants emitting light that they cannot use back out into space. This “flashing” by the biosphere is strongly tied to the rate of photosynthesis, and so provides a measure of how much CO2 plants take in.

NASA pioneered the technology that GeoCarb will carry on an earlier mission, the Orbiting Carbon Observatory 2 (OCO-2). OCO-2 launched into a low Earth orbit in 2014 and has been measuring CO2 from space ever since, passing from pole to pole several times per day as the Earth turns beneath it.

Geostationary satellites like Geo-Carb and the GOES weather satellites (shown here) are positioned over the equator at an altitude of about 36,000 km (or 22,300 miles) above Earth’s surface and orbit at the same speed as the Earth’s rotation, making them appear to stand still. OCO-2, like the Low Earth satellite shown here, samples a much narrower area.
UCAR

Though the instruments are similar, the difference in orbit is crucial. OCO-2 samples a narrow 10-km track over much of the globe on a 16-day repeat cycle, while GeoCarb will look at the terrestrial Western Hemisphere continuously from a fixed position, scanning most of this land mass at least once per day.

Where OCO-2 may miss observing the Amazon for a season due to regular cloud cover, GeoCarb will target the cloud-free regions every day with flexible scanning patterns. Daily revisits will show the biosphere changing in near-real time alongside weather satellites such as GOES 16, which is located at 105 degrees west, helping to connect the dots between the components of Earth’s system.

Nuances of the carbon cycle

Many processes affect levels of CO2 in the atmosphere, including plant growth and decay, fossil fuel combustion and land use changes, such as clearing forests for farming or development. Attributing atmospheric CO2 changes to different processes is difficult using CO2 measurements alone, because the atmosphere mixes CO2 from all of the different sources together.

As mentioned earlier, in addition to CO2 and CH4, GeoCarb will measure CO. Burning fossil fuel releases both CO and CO2. This means that when we see high concentrations of both gases together, we have evidence that they are being released by human activities.

Making this distinction is key so we do not assume that human-induced CO2 emissions come from a decrease in plant activity or a natural release of CO2 from soil. If we can distinguish between man-made and natural emissions, we can draw more robust conclusions about the carbon cycle. Knowing what fraction of these changes is caused by human activities is important for understanding our impact on the planet, and observing and measuring it is essential to any conversation about strategies for reducing CO2 emissions.

GeoCarb’s measurement of methane will be a crucial element in understanding the global carbon-climate system. Methane is produced by natural systems, such as wetlands, and by human activities such as natural gas production. We do not understand the methane portion of the carbon cycle as well as CO2. But just as with CO2, methane observations tell us a lot about the functioning of natural systems. Marshes release methane as part of the natural decay in the system. The rate of release is tied to how wet/dry and warm/cool the system is.

It is uncertain how much natural gas production contributes to methane emissions. One reason to quantify these emissions more accurately is that they represent lost revenue for energy producers. The Environmental Protection Agency estimates a U.S. leakage rate of around 2 percent, which could add up to billions of dollars annually.

These images of the Aliso Canyon, California methane leak, taken 11 days apart in January 2016, are the first time the methane plume from a single facility has been observed from space. Photos were taken by instruments on (left) a NASA ER-2 aircraft at 4.1 miles (6.6 kilometers) altitude, and (right) NASA’s Earth Observing-1 satellite in low-Earth orbit. Future instruments will provide more precise measurements.
NASA

We expect based on simulations that GeoCarb will produce maps that highlight the largest leaks with only a few days of observations. Finding leaks will reduce costs for energy producers and reduce the carbon footprint of natural gas. Currently, energy companies find leaks by sending personnel with detection equipment to suspected leak sites. Newer airborne sensors could make the process cheaper, but they are still deployed on a limited basis and in an ad hoc manner. GeoCarb’s regular observations will provide leakage information to producers in a timely manner to help them limit their losses.

Watching the planet breathe

With daily scans of landmasses in the Western Hemisphere, GeoCarb will provide an unprecedented number of high-quality measurements of CO2, CH4 and CO in the atmosphere. These observations, along with direct measurements of photosynthetic activity from SIF observations, will raise our understanding of the carbon cycle to a new level.

For the first time we will be able to watch as the Western Hemisphere breathes in and out every day, and to see the seasons change through the eyes of the biosphere. Equipped with these observations, we will begin to disentangle natural and human contributions to the carbon balance. These insights will help scientists make robust predictions about Earth’s future.

Berrien Moore III, Vice President, Weather & Climate Programs; Dean, College of Atmospheric & Geographic Sciences; Director, National Weather Center, University of Oklahoma and Sean Crowell, Research Scientist, University of Oklahoma

This article was originally published on The Conversation. Read the original article.

Ethiopia’s inhospitable Danakil Depression gives us clues about life on Mars

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Barbara Cavalazzi, University of Bologna

The Danakil Depression, including the Dallol volcanic area is one of the most remote, inhospitable and poorly studied areas in the world.

They are both found in the Afar Region of Ethiopia and are part of the East African Rift System – an active tectonic plate boundary that’s splitting apart plates at a rate of 7 mm per year. The combination of this area’s geology and environment make it a uniquely extreme place to do research. In collaboration with the Europlanet research team, I am investigating the geological and biological aspects of the Danakil Depression.

Our aim is to study microbes, specifically extremophiles – organisms that thrive in extreme environments. They can live in hot springs, acidic fields, salty lakes and polar ice caps – conditions that would kill humans, animals, and plants. Their existence suggests that life can develop mechanisms to withstand physical and chemical conditions like those on the planet Mars.

There’s no other natural environment like it. What we have found at the site is a combination of extreme physico-chemical parameters. Toxic gases saturate the air, the pH is extremely acidic and saline and metal concentrations are very high.

In these extreme ecosystems we expect to find microbial life in the form of extremophiles, polyextremophiles and potentially new forms of polyextremophiles – these are extremophilic organisms that can tolerate, or adapt, to a combination of physico-chemical parameters.

Harsh environment

This harsh environment was created by the splitting apart of the old African Plate into two plates – the Somali and Nubian Plates. In millions of years, these two plates will be definitively separated and a new ocean basin will form.

Much of the 40km by 10 km Danakil Depression lies between 150-100m below sea level. It’s therefore one of the lowest land areas on Earth. The Dallol volcano, in the northern part of the Danakil Depression, was formed in 1926 by a phreatic eruption. This is when groundwater is heated by magma – essentially, a steam eruption without the lava ejection. Dallol has an elevation of approximately 50m below sea level.

Barbara Cavalazzi collects samples at Dallol.

The Depression is known as the hottest place on Earth. It’s classified as a hyperarid climatic zone and is consistently hot throughout the year. In the Dallol, because of the area’s geothermal activity, the average daily temperature is 45°C. I have registered a temperature there of 55°C – when I had to stop working! The region’s precipitation ranges is very low with an average annual rainfall of only 100-200 mm. In the dry areas of South Africa there would be an average annual rainfall of at least 464mm.

Geothermally heated groundwater rises from the Earth’s crust to the surface, accumulating in the Dallol crater. This creates spectacular and colourful hot springs that are extremely acidic and salty. The area is also characterised by toxic sulphur and chlorine vapours as a result of natural degassing volcanic processes.

What can survive

Living organisms tend to be sensitive to drastic changes in their environments. The cells that make them up can be seriously compromised in extreme physical (relating to temperature, desiccation, radiation, and pressure) and (geo)chemical (such as salinity, pH or heavy metals) conditions.

So what could survive in the Danakil’s harsh environment?

After a detailed study of the area, we have determined that there’s DNA evidence of microbial life. Life that, because of the similar extreme salty environment with volcanic origin, could be what’s surviving on Mars.

The microorganisms able to survive such extreme conditions must be a group of prokaryotes. All living things consist of two cell types: prokaryotes and eukaryotes. Organisms whose cells lack a nucleus and have DNA floating loosely in the liquid centre of the cell are prokaryotes. These are the most common and most ancient forms of life on earth.

What these microorganisms need is liquid water, metabolically suitable carbon, energy, and nutrient sources.

Barbara Cavalazzi, Professor in Geobiology and Astrobiology at the Biological, Geological, and Environmental Sciences-BiGeA of the University of Bologna, Italy, and visiting lecturer at University of Johannesburg, South Africa., University of Bologna

This article was originally published on The Conversation. Read the original article.

Planet or dwarf planet: all worlds are worth investigating

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Tanya Hill, Museum Victoria

Pluto’s status as a “dwarf planet” is once again stirring debate. This comes as some planetary scientists are trying to have Pluto reclassified as a planet – a wish that’s not likely to come true.

Pluto has been known as a dwarf planet for more than a decade. Back in August 2006 astronomers voted to shake up the Solar System, and the number of planets dropped from nine to eight. Pluto was the one cast aside.

There was some outcry that Pluto had been destroyed in an instant and was no longer important, and the reverberations were most keenly felt across America.

After all, Pluto was “their planet”, discovered in 1930 through the meticulous observations of American astronomer Clyde Tombaugh at the Lowell Observatory in Arizona.

At the time of the vote, NASA’s New Horizons spacecraft was only seven months into its nine-year journey to Pluto. There was concern that when it finally arrived, would people even care about a dwarf planet?

For many astronomers, the demotion of Pluto was a defining moment. It wasn’t a gesture of destruction and it wasn’t aimed specifically at Pluto. What it signalled was a major leap forward.

In that moment the world’s astronomers acknowledged significant progress in our understanding of the Solar System, an achievement to be proud of – even if everyone was not entirely happy.

What’s in a name?

The first step to understanding a group of objects is to classify them. We group like with like to examine the aligned characteristics or any significant differences between groups. With this insight comes a deeper understanding of how things work, form or evolve.

The planets were originally grouped together because the ancient Greeks saw them as “the wanderers”, travelling across the sky. Five bright objects – Mercury, Venus, Mars, Jupiter and Saturn – may have looked like stars, but while stars stayed fixed within their constellations, these planets moved independently from them.

The cause of this planetary motion was eventually established by the Polish astronomer Nicolaus Copernicus in the 16th century, bringing with it a new revelation. Planets were more than wanderers, they were objects in orbit about the Sun and with this understanding Earth became a planet too.

Earth became a planet too, once the ‘wanderers’ were understood.
NASA/Reid Wiseman

Defining a planet in the 21st century

More than 400 years and many discoveries later, a new storm began brewing in our understanding of the Solar System.

Since 1992, astronomers had begun to find objects orbiting the Sun out in the realm of Pluto. Were they planets too?

Conversely, Pluto was a bit of an oddball. It was smaller than several moons of other planets, and it had a highly inclined orbit that made it stand out from the others. Was it truly a planet or was it part of a much larger family of objects?

With the discovery of Eris (originally known by its designation 2003 UB313) in 2003, a decision could no longer be avoided. Eris was about the size of Pluto and certainly more massive. Was Eris a planet? And if not, where did that leave Pluto?

Astronomers have a forum for such deliberations via the International Astronomical Union (IAU). Representing astronomers worldwide, the IAU is the recognised authority responsible for naming and classifying planetary bodies and their satellites.

The IAU formed a Planet Definition Committee to consider the scientific, cultural and historical issues at hand. A draft proposal was put forward, and during the 2006 IAU General Assembly in Prague, with the world’s astronomers gathered together, the Committee’s proposal was vigorously debated.

A revised proposal was presented to the IAU membership on the final day of the General Assembly and was passed with a large majority.

Astronomers raise their yellow cards and Pluto becomes a dwarf planet.
Martin George

For the first time, a planet was formally recognised as being “a celestial body that”:

(a) is in orbit around the Sun

(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape

© has cleared the neighbourhood around its orbit.

Since Pluto had not “cleared the neighbourhood around its orbit”, it was not a planet but would be recognised as a “dwarf planet”.

A colleague of mine, Martin George, director of the Launceston Planetarium, was there when the vote was taken and captured the excitement and the nuance of the event.

There was quite a buzz in the room and we knew we were about to make history. Did everyone agree on the exact wording? Perhaps not. However, I think it would have been worse to see media headlines reading ‘Astronomers cannot decide what a planet is’.

Size matters and location too

The distinction of planet and dwarf planet brings a consistency to how objects are named across the universe. On the grand scale, there are galaxies and there are dwarf galaxies.

Within our Milky Way Galaxy, the Sun is a yellow dwarf star that in billions of years will evolve to become a red giant before ending its life as a white dwarf.

The Milky Way and its neighbouring dwarf galaxies, the Large and Small Magellanic Clouds seen in the lower left.
ESO/C. Malin

These distinctions among galaxies and stars helps astronomers interpret and understand them, tracing their evolution.

Planets and dwarf planets are distinct because of their size and their location in the solar system. It provides a way to examine how planets and dwarf planets may have originated and evolved differently.

Planetary resemblance

At present, the IAU has officially recognised five dwarf planets. They are Pluto, Eris, Makemake and Haumea, which orbit the Sun beyond Neptune, and Ceres, which is the only object in the asteroid belt massive enough to be spherical.

The dwarf planets compared to Earth.
NASA

Detractors and also supporters of the standing planet definition can point to problems with it. For instance, it only applies to objects orbiting the Sun. But what about exoplanets? And what is meant by “cleared its neighbourhood”? If Earth was located farther away from the Sun, would it be able to clear its orbit?

But, as astrophysicist Ethan Seigal explains, minor qualifications to the planet definition can bring it in line with exoplanets and allows the definition to work with renewed clarity.

Whereas the latest proposal to reinstate Pluto, advocates a geophysical definition of planet. Namely, that a planet should be large enough to be round, but not so big that it is a star. This broad definition casts the net wide, and not only Pluto, but also the Moon and more than 100 other Solar System objects would become planets.

There are many Solar System objects smaller than Earth.
primefac

Now wouldn’t that be a leap backwards in regards to structuring and understanding our Solar System? How much of it is driven by the notion that nothing but a planet is worth exploration?

There’s a plethora of “not-planets” in our Solar System that are worlds worthy of attention. This includes the fiery volcanoes of Io, the icy geysers of Enceladus, the reddish surface of Makemake, the crazy spin of Haumea and the mystery of hundreds of worlds unknown orbiting beyond Neptune.

So let the official word on planets and dwarf planets be as passed in 2006 and let our exploration of the Solar System continue to amaze us.

Tanya Hill, Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy), Museum Victoria

Fly me to the Moon? Why the world should be wary of Elon Musk’s space race

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Alan Marshall, Mahidol University

Want to fly to the moon? Well, now you won’t have to bother with all those years of rigorous astronaut training – all you need is a huge wad of cash. Elon Musk, technopreneur, has built a small spaceship called Dragon and if you slap down enough money – maybe a hundred million dollars or so – he’ll fly you to the Moon.

The first flight is set for 2018, a target so ambitious it verges on the incredible.

Musk’s moonshot plan has been greeted enthusiastically by most space fans but some are a little doubtful. Other commentators remain totally uninspired, ridiculing the idea as a gigantic waste of money.

This ambivalence isn’t surprising really, since history shows that soon after the Apollo 11 moon landing in 1969, people switched their televisions to more down-to-earth events while wondering why NASA kept going back to the Moon again and again with Apollo 12, then Apollo 13, then Apollo 14 – all the way up to Apollo 17.

Natural process, or a social one?

Musk would tell you he’s not using taxpayer funds for his moonshot and that his SpaceX venture is a private commercial business. But SpaceX’s only significant customer so far has been NASA – a taxpayer-funded agency that pays it to deliver cargo to the International Space Station.

And even before SpaceX had delivered anything, NASA made a massive investment in the firm to get it up and running. Any claim that SpaceX is purely a commercial business, then, is also incredible.

Like many space fans, Musk will tell you that this moonshot is the first step in the “natural process” of human space expansion. The next steps involve the colonisation of the Moon and then Mars.

But space travel is not a natural process; it’s a social process involving domestic politics, international competition, the marketing of patriotic heroism, and the divvying up of state funds.

Harkening back to the dark past

The “colonisation” theme of space expansion is also problematic since it signifies a potential re-emergence of the social injustices and environmental disasters wrought by past colonial ventures. Being a fan of “space colonisation”, then, can be likened to rejoicing in the displacement of native peoples and celebrating the destruction of wilderness.

Unfortunately, too often space expansion has utilised historic conquests to map out the future; witness Star Trek’s Space: the Final Frontier theme, or Musk’s own idea to colonise Mars.

Calling for a new “age of exploration” in space recalls past voyages of discovery ignores how Chritopher Columbus decimated native tribes with smallpox and how Spanish conquistadors ransacked Meso-America’s temples to loot gold.

Space fans might argue that there are no people in space to be colonised, that the Moon and Mars are uninhabited lands. But the plan to settle Mars, for example, and then to set about extracting valuable resources without working out if some alien species is living there – even if those life forms are microbial – seems reckless.

It also smacks of anthropocentrism since humans will doubtless carry to Mars the attitude that microbes are lower lifeforms and that it’s OK to stomp all over their planet spreading pollution and mucking up their environment.

Even if they are lifeless, we should consider that the Moon and Mars belong to all of us; they are the common heritage of humankind. And those who first to get to the Moon or to Mars shouldn’t be permitted to plunder these worlds just for the sake of their own adventure or profit.

An alliance of interests

One prominent fan of American space expansion is US President Donald Trump. “Space is terrific,” he said in Florida last year. Trump also called for more space exploration in his recent speech to Congress.

Many scientists are wary of Trump’s attitude to science but, in a surprising willingness to embrace both science and the wider universe beyond America, the president wants NASA to “explore the mysteries of deep space”.

In the process, Trump is also working out how to rid NASA of the those pesky climate scientists who, he claims, are peddling “politicised” science.

Trump met Elon Musk within days of assuming the presidency and, with their shared love of capitalism and penchant for self-promotion, they seem to be entering a working relationship, described by some as cronyism.

Trump seems willing to support Musk if the entrepreneur can help Make America Great Again by shooting Americans off to the Moon before China gets there. Musk may seem confident about his 2018 plans because he believes he has presidential blessing.

A note of caution

But perhaps it’s too soon to worry about Moon grabs or Martian colonialism.

First, both Trump and Musk are notorious “big talkers” and they may be playing with the macho spectacle of space travel. If their space plans gurgle into an economic sinkhole, they’ll probably quietly abandon them.

And the 2018 moonshot is not going to actually land on the Moon; it’s merely going to shoot around it and then head back to Earth. Nobody will get the chance to plant a flag.

Space tourism, moon bases and Martian colonies have all been predicted for decades and nothing has ever come of them. Wernher von Braun, the Apollo rocket hero (and ex-Nazi) showcased such prospective space endeavours on a television show with Walt Disney in the 1950s (using whizzing Disney graphics). But 70 years later, a space colony is nowhere to be found.

An outright Moon grab would also be illegal, since the 1967 UN Outer Space Treaty forbids such acts. The US has re-interpreted this treaty to suggest that it permits resource extraction from the Moon and the planets in the Solar System, but not all nations accept this view.

Not what we all want

If Musk does get his rich clients to circle the Moon next year, and then manages to set up bases and colonies on the lunar surface and then Mars, it won’t be because he’s made a business success out of space expansion. And it won’t be due to the scientific merit of moon bases.

Rather, it will be because he has managed to dupe the American taxpayer with expensive technological fantasies and because he’s broken the ideal of the common heritage of mankind enshrined in international law. Humanity and the Earth will be diminished in the process.

It’s possible the cosmos will be diminished and despoiled too with mining firms digging up the moonscape, rocket fuel spilled all over the Martian surface, and neon lights flashing in shiny space casinos.

Of course, some space fans believe the only way they’ll realise their space fantasies is to ride behind the glory of “visionaries” such as Musk – and the unknown mega-rich space passengers set to shoot off around the Moon next year.

But the Earth abounds with those willing to poke fun at such showy space adventures, which is good – Musk needs to know that not everybody is on board.

Alan Marshall, Lecturer in Environmental Social Sciences, Faculty of Social Sciences and Humanities, Mahidol University

This article was originally published on The Conversation. Read the original article.

It’s our Solar System in miniature, but could TRAPPIST-1 host another Earth?

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Elizabeth Tasker, Japan Aerospace Exploration Agency (JAXA)

Scientists have discovered seven Earth-sized planets, so tightly packed around a dim star that a year there lasts less than two weeks. The number of planets and the radiation levels they receive from their star, TRAPPIST-1, make these worlds a miniature analogue of our own Solar System.

The excitement surrounding TRAPPIST-1 was so great that the discovery was announced with an article in Nature accompanied by a NASA news conference. In the last two decades, nearly 3,500 planets have been found orbiting stars beyond our Sun, but most don’t make headlines.

How likely are we really to find a blue marble like our Earth among these new worlds?

Earth 2.0?

We still know little about these planets with certainty, but initial clues look enticing.

All seven worlds complete an orbit in between 1.5 and 13 days. So closely are they huddled that a person standing on one planet might see the neighbouring worlds in the sky even larger than our Moon. The short years place the planets closer to their star than any planet sits to the Sun. Happily, they avoid being baked by TRAPPIST-1 because it is incredibly dim.

TRAPPIST-1 is a small ultracool dwarf star with a luminosity roughly 1/1000th that of the Sun. Comparing the two at Wednesday’s news conference, lead author of the Nature paper, Michaël Gillon, said that if the Sun were scaled to the size of a basketball, TRAPPIST-1 would be a puny golf ball. The resulting paltry amount of heat means that three of the seven TRAPPIST-1 planets actually receive similar amounts of radiation as Venus, Earth and Mars.

This alternative Solar System does look like a compact version of our own, but does TRAPPIST-1 include an Earth 2.0?

Artists impression of the seven TRAPPIST-1 worlds, compared to our solar system’s terrestrial planets.
NASA/JPL-Caltech

Here’s the good news first.

The seven siblings are all Earth-sized, with radii between three quarters and one times that of our home planet and masses that range from roughly 50% to 150% of Earth’s (the mass of the outermost world remains uncertain).

Because all are smaller than 1.6 times Earth’s radius, the seven TRAPPIST-1 planets are likely to be rocky worlds, not gaseous Neptunes. TRAPPIST-1d, e and f are within the star’s temperate region — aka the “Goldilocks zone” where it’s not too hot and not too cold — where an Earth-like planet could support liquid water on its surface.

The orbits of the six inner planets are nearly resonant, meaning that in the time it takes for the innermost planet to orbit the star eight times, its outer siblings make five, three and two orbits.

Such resonant chains are expected around stars where the planets have moved from where they originally formed. This migration occurs when the planets are still young and embedded in the star’s gaseous planet-forming disc. As the gravity of the young planet and the gas disc pull on one another, the planet’s orbit can change, usually moving towards the star.

If multiple planets are in the system, their gravity also pulls on one another. This nudges the planets into resonant orbits as they migrate through the gas disc. The result is a string of resonant planets close to the star, just like that seen encircling TRAPPIST-1.

Being born far from the star offers a couple of potential advantages. Dim stars like TRAPPIST-1 are irritable when young, emitting flares and high radiation that may sterilise the surface of nearby planets. If the TRAPPIST-1 system did indeed form further away and migrate inwards, its worlds may have avoided getting fried.

Originating where temperatures are colder would also mean the planets formed with a large fraction of ice. As the planets migrate inwards, this ice could melt into an ocean. This notion is supported by the estimated densities of the planets, which are low enough to suggest volatile-rich compositions, like water or a thick atmosphere.

Not an Earth?

Since our search for extraterrestrial life focuses on the presence of water, melted icy worlds seem ideal.

But this may actually bode ill for habitability. While 71% of the Earth’s surface is covered by seas, water makes up less than 0.1% of our planet’s mass. A planet with a high fraction of water may become a water world: all ocean and no exposed land.

Deep water could also mean there’s a thick layer of ice on the ocean floor. With the planet’s rocky core separated from both air and sea, no carbon-silicate cycle could form – a process that acts as a thermostat to adjust the level of warming carbon dioxide in the air on Earth.

If the TRAPPIST-1 planets can’t compensate for different levels of radiation from their star, the temperate zone for the planet shrinks to a thin strip. Any little variation, from small ellipicities in the planet’s orbit to variations in the stellar brightness, could turn the world into a snowball or baked desert.

Jupiter’s moon Io, is in resonance with moons Europa and Ganymede, and its tidal heating powers its volcanoes.
NASA/JPL/University of Arizona

Even if the oceans were sufficiently shallow to avoid this fate, an icy composition might produce a very strange atmosphere. On the early Earth, air was spewed out in volcanic plumes. If a TRAPPIST-1 planet’s interior is more akin to a giant comet than to a silicate-rich Earth, the air expelled risks being rich in the greenhouse gases of ammonia and methane. Both trap heat at the planet’s surface, meaning the best location for liquid water might actually be in a region cooler than the “Goldilocks zone”.

Finally, the TRAPPIST-1 system’s orbits are problematic. Situated so close to the star, the planets are likely in tidal lock – with one face permanently turned towards the star – resulting in perpetual day on one side and everlasting night on the other.

Not only would this be weird to experience, the associated extremes of temperatures could also evaporate all water and collapse the atmosphere if the planet’s winds are unable to redistribute heat.

Also, even a small ellipticity in the planets’ seemingly circular orbits could power a second kind of warmth, called tidal heating, making the planets into Venus-like hothouses. Slight elongations in the planet’s path around its star would cause the pull from the star’s gravity to strengthen and weaken during its year, flexing the planet like a stress ball and generating tidal heat.

This process occurs on three of Jupiter’s largest moons whose mildly elliptical paths are caused by resonant orbits similar to the TRAPPIST-1 worlds. In Europa and Ganymede, the flexing heat allows subsurface liquid oceans to exist. But Jupiter’s innermost moon, Io, is the most volcanic place in our Solar System.

If the TRAPPIST-1 planets’ orbits are similarly bent, they could turn out to be sweltering.

The view from here

So how will we ever know what the TRAPPIST-1 planets are really like? To investigate the possible scenarios, we need to take a look at the atmosphere of the TRAPPIST-1 siblings.

TRAPPIST-1 was named for the Belgian 60cm TRAnsiting Planets and Planetesimal Small Telescope in Chile that detected the star’s first three planets last year (it also happens to be the name of a type of Belgian beer). As the name suggests, both the original three worlds and four new planetary siblings were discovered using the transit technique; the tiny dip in starlight as the planets passed between the star and the Earth.

Transiting makes the planets excellent candidates for the next generation of telescopes with their ability to identify molecules in the planet’s air as starlight passes through the gas. The next five years may therefore give us the first real look at a rocky planet with a very different history to anything in our Solar System.

Thomas Zurbuchen, associate administer of the Science Mission Directorate at NASA, declared the discovery of TRAPPIST-1 as, “A leap forward to answering ‘are we alone?’”.

But the real treasure of TRAPPIST-1 is not the possibility that the planets may be just like the one we call home; it’s the exciting thought that we might be looking at something entirely new.

Elizabeth Tasker, Associate Professor, Japan Aerospace Exploration Agency (JAXA)

This article was originally published on The Conversation. Read the original article.

Tiny satellites poised to make big contributions to essential science

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Tiny satellites, some smaller than a shoe box, are currently orbiting around 200 miles above Earth, collecting data about our planet and the universe. It’s not just their small stature but also their accompanying smaller cost that sets them apart from the bigger commercial satellites that beam phone calls and GPS signals around the world, for instance. These SmallSats are poised to change the way we do science from space. Their cheaper price tag means we can launch more of them, allowing for constellations of simultaneous measurements from different viewing locations multiple times a day – a bounty of data which would be cost-prohibitive with traditional, larger platforms.

Called SmallSats, these devices can range from the size of large kitchen refrigerators down to the size of golf balls. Nanosatellites are on that smaller end of the spectrum, weighing between one and 10 kilograms and averaging the size of a loaf of bread.

Starting in 1999, professors from Stanford and California Polytechnic universities established a standard for nanosatellites. They devised a modular system, with nominal units (1U cubes) of 10x10x10 centimeters and 1kg weight. CubeSats grow in size by the agglomeration of these units – 1.5U, 2U, 3U, 6U and so on. Since CubeSats can be built with commercial off-the-shelf parts, their development made space exploration accessible to many people and organizations, especially students, colleges and universities. Increased access also allowed various countries – including Colombia, Poland, Estonia, Hungary, Romania and Pakistan – to launch CubeSats as their first satellites and pioneer their space exploration programs.

Initial CubeSats were designed as educational tools and technological proofs-of-concept, demonstrating their ability to fly and perform needed operations in the harsh space environment. Like all space explorers, they have to contend with vacuum conditions, cosmic radiation, wide temperature swings, high speed, atomic oxygen and more. With almost 500 launches to date, they’ve also raised concerns about the increasing amount of “space junk” orbiting Earth, especially as they come almost within reach for hobbyists. But as the capabilities of these nanosatellites increase and their possible contributions grow, they’ve earned their own place in space.

From proof of concept to science applications

When thinking about artificial satellites, we have to make a distinction between the spacecraft itself (often called the “satellite bus”) and the payload (usually a scientific instrument, cameras or active components with very specific functions). Typically, the size of a spacecraft determines how much it can carry and operate as a science payload. As technology improves, small spacecraft become more and more capable of supporting more and more sophisticated instruments.

These advanced nanosatellite payloads mean SmallSats have grown up and can now help increase our knowledge about Earth and the universe. This revolution is well underway; many governmental organizations, private companies and foundations are investing in the design of CubeSat buses and payloads that aim to answer specific science questions, covering a broad range of sciences including weather and climate on Earth, space weather and cosmic rays, planetary exploration and much more. They can also act as pathfinders for bigger and more expensive satellite missions that will address these questions.

I’m leading a team here at the University of Maryland, Baltimore County that’s collaborating on a science-focused CubeSat spacecraft. Our Hyper Angular Rainbow Polarimeter (HARP) payload is designed to observe interactions between clouds and aerosols – small particles such as pollution, dust, sea salt or pollen, suspended in Earth’s atmosphere. HARP is poised to be the first U.S. imaging polarimeter in space. It’s an example of the kind of advanced scientific instrument it wouldn’t have been possible to cram onto a tiny CubeSat in their early days.

HARP spacecraft and payload at different stages of development.
Spacecraft: SDL, Payload:UMBC, CC BY-ND

Funded by NASA’s Earth Science Technology Office, HARP will ride on the CubeSat spacecraft developed by Utah State University’s Space Dynamics Lab. Breaking the tradition of using consumer off-the-shelf parts for CubeSat payloads, the HARP team has taken a different approach. We’ve optimized our instrument with custom-designed and custom-fabricated parts specialized to perform the delicate multi-angle, multi-spectral polarization measurements required by HARP’s science objectives.

HARP is currently scheduled for launch in June 2017 to the International Space Station. Shortly thereafter it will be released and become a fully autonomous, data-collecting satellite.

SmallSats – big science

HARP is designed to see how aerosols interact with the water droplets and ice particles that make up clouds. Aerosols and clouds are deeply connected in Earth’s atmosphere – it’s aerosol particles that seed cloud droplets and allow them to grow into clouds that eventually drop their precipitation.

Pollution particles lead to precipitation changes.
Martins, UMBC, CC BY-ND

This interdependence implies that modifying the amount and type of particles in the atmosphere, via air pollution, will affect the type, size and lifetime of clouds, as well as when precipitation begins. These processes will affect Earth’s global water cycle, energy balance and climate.

When sunlight interacts with aerosol particles or cloud droplets in the atmosphere, it scatters in different directions depending on the size, shape and composition of what it encountered. HARP will measure the scattered light that can be seen from space. We’ll be able to make inferences about amounts of aerosols and sizes of droplets in the atmosphere, and compare clean clouds to polluted clouds.

In principle, the HARP instrument would have the ability to collect data daily, covering the whole globe; despite its mini size it would be gathering huge amounts of data for Earth observation. This type of capability is unprecedented in a tiny satellite and points to the future of cheaper, faster-to-deploy pathfinder precursors to bigger and more complex missions.

HARP is one of several programs currently underway that harness the advantages of CubeSats for science data collection. NASA, universities and other institutions are exploring new earth sciences technology, Earth’s radiative cycle, Earth’s microwave emission, ice clouds and many other science and engineering challenges. Most recently MIT has been funded to launch a constellation of 12 CubeSats called TROPICS to study precipitation and storm intensity in Earth’s atmosphere.

For now, size still matters

But the nature of CubeSats still restricts the science they can do. Limitations in power, storage and, most importantly, ability to transmit the information back to Earth impede our ability to continuously run our HARP instrument within a CubeSat platform.

So as another part of our effort, we’ll be observing how HARP does as it makes its scientific observations. Here at UMBC we’ve created the Center for Earth and Space Studies to study how well small satellites do at answering science questions regarding Earth systems and space. This is where HARP’s raw data will be converted and interpreted. Beyond answering questions about cloud/aerosol interactions, the next goal is to determine how to best use SmallSats and other technologies for Earth and space science applications. Seeing what works and what doesn’t will help inform larger space missions and future operations.

The SmallSat revolution, boosted by popular access to space via CubeSats, is now rushing toward the next revolution. The next generation of nanosatellite payloads will advance the frontiers of science. They may never supersede the need for bigger and more powerful satellites, but NanoSats will continue to expand their own role in the ongoing race to explore Earth and the universe.

J. Vanderlei Martins, Professor of Physics, University of Maryland, Baltimore County

This article was originally published on The Conversation. Read the original article.

Hubble Rocks with a Heavy-Metal Home

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This 10.5-billion-year-old globular cluster, NGC 6496, is home to heavy-metal stars of a celestial kind! The stars comprising this spectacular spherical cluster are enriched with much higher proportions of metals — elements heavier than hydrogen and helium are curiously known as metals in astronomy — than stars found in similar clusters.

A handful of these high-metallicity stars are also variable stars, meaning that their brightness fluctuates over time. NGC 6496 hosts a selection of long-period variables — giant pulsating stars whose brightness can take up to, and even over, a thousand days to change — and short-period eclipsing binaries, which dim when eclipsed by a stellar companion.

The nature of the variability of these stars can reveal important information about their mass, radius, luminosity, temperature, composition, and evolution, providing astronomers with measurements that would be difficult or even impossible to obtain through other methods.

NGC 6496 was discovered in 1826 by Scottish astronomer James Dunlop. The cluster resides at about 35,000 light-years away in the southern constellation of Scorpius (The Scorpion).

Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt
Text credit: European Space Agency