Rover Driver Scott Maxwell with a model of MER. Photo courtesy Scott Maxwell
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How often have you wanted to be a fly on the wall during media interviews of top scientists and engineers? Here’s your chance! On Friday, February 10, we’ll be having our first live interview via a Google+ Hangout On Air. We’ve done the weekly Space Hangout for several weeks now and Fraser has done multiple virtual star parties via a Hangout On Air. Now we’ll start the first of what we hope are many live interviews that we’ll share with our readers and fans. We’re excited that Mars rover driver Scott Maxwell, will be joining us, and he will provide insight on the plans for the Opportunity rover’s upcoming winter, a look back at the 8 years and counting for the rovers, a look ahead to the future, and more.
The Hangout On Air will start at 18:00 UTC (1 pm EST,12 noon CST, 10 am PST) or you can check here at the fancy-schmancy time and date announcement Scott put together that shows the time in almost every time zone possible.
How do you find the Hangout? The best way is to join Google+ and “circle” Fraser and the Hangout On Air will show up in his timeline. You can also circle Nancy, who will also provide a link, but within Fraser’s timeline there will also be the opportunity for you to post questions that we can ask Scott during the live interview.
If you can’t watch live, the Hangout will be recorded and we’ll post it later on Friday on Universe Today.
1st Color image of Spirit lander and Bonneville Crater from Mars orbit. Near the lower left corner of this view is the three-petal lander platform that NASA's Mars Exploration Rover Spirit drove off in January 2004. Credit: NASA/JPL-Caltech/Univ. of Arizona
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The Lander platform for NASA’s Spirit rover has been photographed in stunning high resolution color for the first time from Mars orbit – just over 8 years after the now legendary robot survived the scorching atmospheric heat of the 6 minute plunge through the Martian atmosphere and bounced to a stop inside Gusev Crater on January 3, 2004.
Spirit’s three petaled landing pad was finally imaged in color by NASA’s powerful Mars Reconnaissance Orbiter (MRO) spacecraft just days ago on January 29, 2012 at 3:04 p.m. local Mars time.
The MRO spacecraft was soaring overhead and captured the image of Spirit’s lander with the high resolution HiRISE camera from a distance of some 262 kilometers, (162 miles).
“HiRISE has never before imaged the actual lander for the Spirit rover in color, [located] on the west side of Bonneville Crater,” writes Alfred McEwen, HiRISE Principal Investigator at the University of Arizona.
1st Color image of Spirit Lander and Bonneville Crater from Mars orbit
Spirit landing pad at lower left; Bonneville Crater rim at top right.
Credit: NASA/JPL/UA/HiRISE
While protectively cocooned inside the airbag cushioned lander, Spirit bounced about two dozen times before rolling to rest on the Martian plains about ¼ mile away from Bonneville Crater. Then her landing petals unfurled, the airbags were partially retracted and Spirit eventually drove off the landing pad.
“The lander is still bright, but with a reddish color, probably due to a [Martian] dust cover.”
Spirit rover images her Lander Platform after Egress
- Now imaged for the 1st time from Mars orbit by NASA’s MRO spacecraft. Lander had 3-petals and airbags. Credit: NASA/JPL-Caltech/Cornell
Spirit initially drove to Bonneville Crater and circumnavigated part way around the rim before speeding off towards the Columbia Hills, about 2 miles to the East. She eventually scaled the summit of Husband Hill and drove down the opposite side to the Home Plate” volcanic feature where she rests today – see travse map below.
“A bright spot from a remnant of the heat shield is still visible on the north rim of Bonneville Crater. The backshell and parachute are still bright, but were not captured in the narrow color swath.”
“The rover itself can still be seen near “Home Plate” in the Columbia Hills, but there is no obvious sign of rover tracks–erased by the wind,” McEwen notes.
Here is a photo taken by Spirit looking back to the lander – now imaged in color from orbit for the first time – for a comparative view, before she drove off forever.
Spirit endured for more than six years of bonus time exploration beyond her planned 90 day mission. And Opportunity is still roving Mars today !
Spirit Rover traverse map from Gusev Crater landing site near Bonneville Crater to Columbia Hills to Home Plate: 2004 to 2011. Credit: NASA/JPL/UA/HiRISE
Curiosity – NASA’s newest, biggest ever and maybe last Mars rover – is speeding through interplanetary space for an August 2012 landing inside Gale Crater.
Read my 8th Year Anniversary articles about Spirit and Opportunity on Mars – here and here
The Phoenix lander still visible at Mars north polar region, nearly 4 Earth years and 2 Mars years after the spacecraft landed on Mars. Credit: NASA/JPL/University of Arizona
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I spy Phoenix! said the HiRISE camera on board the Mars Reconnaissance Orbiter! This new image acquired on January 26, 2012 shows that the Phoenix lander and its backshell are still visible from Mars’ orbit. The parachute, seen in earlier images, is probably about 130 meters south of where this picture ends. This is one of a series of images to monitor frost patterns at the Phoenix landing site, said HiRISE Principal Investigator, Alfred McEwen, adding that this new images shows almost the same appearance of the hardware as 1 Mars years ago, in 2010. See larger versions of this image at the HiRISE website.
See below for comparison images from orbit from 2008, shortly after Phoenix landed and 2010, after the mission had ended.
Two images of the Phoenix Mars lander taken from Martian orbit in 2008 and 2010. The 2008 lander image shows two relatively blue spots on either side corresponding to the spacecraft's clean circular solar panels. In the 2010 image scientists see a dark shadow that could be the lander body and eastern solar panel, but no shadow from the western solar panel. Image credit: NASA/JPL-Caltech/University of Arizona
In these images, also from the Mars Reconnaissance Orbiter, signs of severe ice damage to the lander’s solar panels show up in the 2010 image, with one panel appearing to be completely gone. The Phoenix team says this is consistent with predictions of how Phoenix could be damaged by harsh winter conditions. It was anticipated that the weight of a carbon-dioxide ice buildup could bend or break the solar panels.
An avalanche on Mars captured by the HiRISE camera on the Mars Reconnaissance Orbiter on November 27, 2011. Credit: NASA/JPL/University of Arizona.
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Its avalanche season on Mars! And once again the HiRISE camera on the Mars Reconnaissance Orbiter has captured an avalanche taking place on a steep cliff or scarp in Mars’ north polar region. Back in 2008, the HiRISE team created quite a sensation when it captured an avalanche in action on Mars. The high resolution camera did it again in 2010 when springtime arrived once more. Now, another Mars year later, the team has been monitoring specific areas, looking for evidence of avalanches and they hit pay dirt – literally. This image of an avalanche taking place is from a large image “strip” from HiRISE taken in the extreme northern latitude of Mars, about 85 degrees north.
Dust, fine-grained ice and possibly large blocks of either regolith or rocks has detached from a steep, towering cliff and cascaded below. The HiRISE team say the occurrence of avalanches is spectacularly revealed by the accompanying clouds of fine material that continue to settle out of the air.
The avalanches are a result of carbon-dioxide frost that clings to the scarp in the darkness of winter, and when sunlight hits them in the spring they loosen up and fall.
These events happen mostly in the middle of spring, roughly equivalent to April to early May on Earth. And it seems this is a regular spring process at Mars’ north pole that may be expected every year.
This image is part of the latest PDS release from HiRISE.
View of Mars' surface near the north pole from the Phoenix lander. Polygon shapes can be seen in the soil. Credit: NASA/JPL-Calech/University of Arizona
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Mars is often referred to as a desert world, and for good reason – its surface is barren, dry and cold. While water was abundant in the distant past, it has long since disappeared from the surface, although ice, snow, frost and fog are still common. Other than liquid brines possibly trickling at times, all of Mars’ remaining water is now frozen in permafrost and in the polar ice caps. It has long been thought that the harsh conditions would make current life unlikely at best, and now a new study reaffirms that view.
The results come from continued analysis of the data from the Phoenix lander mission, which landed in the arctic region near the north pole of Mars in 2008. They suggest that Mars has experienced a prolonged drought for at least the past 600 million years.
According to Dr. Tom Pike from Imperial College London, “We found that even though there is an abundance of ice, Mars has been experiencing a super-drought that may well have lasted hundreds of millions of years. We think the Mars we know today contrasts sharply with its earlier history, which had warmer and wetter periods and which may have been more suited to life. Future NASA and ESA missions that are planned for Mars will have to dig deeper to search for evidence of life, which may still be taking refuge underground.”
The team reached their conclusions by studying tiny microscopic particles in the soil samples dug up by Phoenix, which had been photographed by the lander’s atomic-force microscope. 3-D images were produced of particles as small as 100 microns across. They were searching specifically for clay mineral particles, which form in liquid water. The amount found in the soil would be a clue as to how long the soil had been in contact with water. It was determined that less than 0.1 percent of the soil samples contained clay particles, pointing to a long, arid history in this area of Mars.
Since the soil type on Mars appears to be fairly uniform across the planet, the study suggests that these conditions have been widespread on the planet, and not just where Phoenix landed. It’s worth keeping in mind though that soil particles and dust on Mars can be distributed widely by sandstorms and dust devils (and some sandstorms on Mars can be planet-wide in size). The study also implies that Mars’ soil may have only been exposed to liquid water for about 5,000 years, although some other studies would tend to disagree with that assessment.
It should also be noted that more significant clay deposits have been found elsewhere on Mars, including the exact spot where the Opportunity rover is right now; these richer deposits would seem to suggest a different history in different regions. Because of this, and for the other reasons cited above, it may be premature then to extrapolate the Phoenix results to the entire planet, similar soil types notwithstanding. While this study is important, more definitive results might be obtained when physical soil samples can actually be brought back to Earth for analysis, from multiple locations. More sophisticated rovers and landers like the Curiosity rover currently en route to Mars, will also be able to conduct more in-depth analysis in situ.
The Phoenix soil samples were also compared to soil samples from the Moon – the distribution of particle sizes was similar between the two, indicating that they formed in a similar manner. Rocks on Mars are weathered down by wind and meteorites, while on the airless Moon, only meteorite impacts are responsible. On Earth of course, such weathering is caused primarily by water and wind.
As for the life question, any kind of surface dwelling organisms would have to be extremely resilient, much like extremophiles on Earth. It should be kept in mind, however, that these results apply to surface conditions; it is still thought possible that any early life on the planet could have continued to thrive underground, protected from the intense ultraviolet light from the Sun, and where some liquid water could still exist today.
Given Mars’ much wetter early history, the search for evidence of past or present life will continue, but we may have to dig deep to find it.
A 3-d view of a well-preserved and unnamed impact crater on Mars, as seen by the HiRISE camera on the Mars Reconnaisancee Orbiter. Credit: NASA/JPL/University of Arizona. Click for high-resolution version.
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This is why I always keep a pair of 3-D glasses by my computer. This well-preserved crater on Mars may look like just your average, run-of-the-mill impact crater in 2-D, but in 3-D, the sharply raised rim, the deep, cavernous crater body, and especially the steep crater walls will have you grabbing your armchairs so you don’t fall in. The image is courtesy of the HiRISE camera team from the Mars Reconnaissance Orbiter. This unnamed crater is about 6 or 7 kilometers wide from rim to rim. HiRISE took the image on New Year’s Eve 2011.
HiRISE principal investigator Alfred McEwen says that the camera has imaged hundreds of well-preserved impact craters on Mars ranging from 1 meter to more than 100 kilometers wide. What can the scientists learn from craters?
“These targets are of great interest for multiple reasons,” he said. “First, we want to better understand impact cratering, a fundamental surface process. Second, such craters often contain good exposures of bedrock in the steep walls and, if the crater is large enough, in the central uplift. Just like terrestrial geologists are attracted to good bedrock outcrops like road cuts, planetary geologists are attracted to well-preserved craters.
“Third, the steep slopes often reveal active processes, such as formation of gullies, boulder falls, and slope streaks that could form in a variety of ways. Some of these active processes could be related to water, since the crater may expose lenses of ice or salty water, or create deep shadows that trap volatiles, or expose salts that can extract water from the air.”
Plus, they are just plain wonderful to behold, especially in the resolution the HiRISE can obtain.
A non-3-D version of the same image. Credit: NASA/JPL/University of Arizona
Poster art for the Russian Phobos-Grunt mission. Russian Federal Space Agency)/IKI
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Russia says “eish odin ras”* for its Mars moon lander mission, according to Roscomos chief Vladimir Popovkin.
If the European Space Agency does not include Russia in its ExoMars program, a two-mission plan to explore Mars via orbiter and lander and then with twin rovers (slated to launch in 2016 and 2018, respectively), Roscosmos will try for a “take-two” on their failed Phobos-Grunt mission.
“We are holding consultations with the ESA about Russia’s participation in the ExoMars project… if no deal is reached, we will repeat the attempt,” said Popovkin on Tuesday.
Phobos-Grunt, an ambitious mission to land on the larger of Mars’ two moons, collect samples and return them to Earth, launched successfully on November 9, 2011. It became caught in low-Earth orbit shortly afterwards, its upper-stage engines having failed to ignite.
After many attempts to communicate with the stranded spacecraft, Phobos-Grunt re-entered the atmosphere and impacted on January 15. Best estimates place the impact site in the Pacific Ocean off the coast of southern Chile.
The failed mission also included a Chinese orbiter and a life experiment from The Planetary Society.
Russia is offering ESA the use of a Proton launch vehicle for inclusion into the ExoMars mission, now that the U.S. has canceled its joint participation and Atlas carrier. Roscomos and ESA are scheduled to discuss the potential partnership in February.
Topographic map from Mars Global Surveyor showing colour-coded altitudes; the blue areas are the lowest and correspond to the possible ancient ocean in the northern hemisphere. Credit: NASA/JPL
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For a long time now, evidence has continued to indicate that Mars was once a water world – near-surface groundwater, lakes, rivers, hot springs and, according to some planetary models, even an ancient ocean in the northern hemisphere. That last one in particular has been a subject of intense debate; some scientists see evidence for it while others do not. Even if it was there, it may have been a warm ocean or it may have been colder, like the polar seas here on Earth. The prospect of an ocean of any kind on early Mars is an exciting one, regarding the question of possible life way back then. The argument has swung both ways over the years, but now another new report has been published which comes down on the “yes” side.
The results come from the Mars Express Orbiter – specifically its ground-penetrating radar (MARSIS) and they have just been published in Geophysical Research Letters by Jérémie Mouginot from the University of California. The findings reinforce the idea of a large ocean which occupied much of the northern hemisphere, also known as Oceanus Borealis.
The radar has mapped the sedimentary deposits within the region, known as the Vastitas Borealis Formation, which are about 100 metres (328 feet) thick and overlie deeper volcanic deposits. Significantly, the mapping of the dielectric constant showed that the sedimentary deposits left over from the putative ocean differ from volcanic rock – they have a value of about 4-5, while volcanic deposits have a value of 9, 10 or even higher. Pure ice has a value of 3.1.
According to the research team, “Although much is still unknown about the evolution and environmental context of a Late Hesperian ocean, our observations provide persuasive evidence of its existence by the measurement of a dielectric constant of the Vastitas Borealis Formation that is sufficiently low that it can only be explained by the widespread deposition of (now desiccated) aqueous sediments or sediments mixed with massive ice.”
The big question has always been, if there was an ocean, where did all the water go? Additional radar mapping from Mars Express has shown that there are massive amounts of water ice buried beneath the surface, notably at the poles as well as within the speculative shorelines of the old ocean and even closer to the equator than was previously thought. It might seem reasonable to conclude then that much of the water from the ocean, and perhaps other seas or lakes as well, is still there, but now frozen solid.
It’s interesting to note also that the Phoenix lander, which landed within the Vastitas Borealis Formation in 2008, found water ice deposits only a few centimetres below the surface.
“As such, the formation represents the best geologic evidence to date for the existence of an ocean in the Late Hesperian, about 3 billion years ago,” the researchers said.
From the abstract:
A number of observations suggest that an extended ocean once covered a significant part of the Martian northern hemisphere. By probing the physical properties of the subsurface to unprecedented depth, the MARSIS/Mars Express provides new geophysical evidences for the former existence of a Late Hesperian ocean. The Vastitas Borealis formation, located inside a putative shoreline of the ancient ocean, has a low dielectric constant compared with that of typical volcanic materials. We show that the measured value is only consistent with low-density sedimentary deposits, massive deposits of ground-ice, or a combination of the two. In contrast, radar observations indicate a distribution of shallow ground ice in equilibrium with the atmosphere in the south polar region. We conclude that the northern plains are filled with remnants of a late Hesperian ocean, fed by water and sediments from the outflow channels about 3 Gy ago.
The full article can be purchased here ($25.00 U.S.).
New estimates of water ice on Mars suggest there may be large reservoirs of underground ice at non-polar latitudes. The map here shows "water-equivalent hydrogen". Oranges and reds on the map (values greater than 4.5 weight % water-equivalent hydrogen at the surface) point out areas where the amount of deeply buried water ice is greater than what can fit in the pore spaces of the surface rocks. Image credit: Feldman et al., 2011
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Many models predict that water ice shouldn’t be stable on Mars today, anywhere beyond the poles, no matter how deep you bury it. And yet, a recently published study shows that large regions outside the polar areas may, in fact, contain a relative abundance of water. This is exciting, not only because water has implications for the possibility of life on Mars, but also because it can provide a valuable resource to future explorers, both as a fuel and for life support. And if this water is near the equator, that makes it much easier to get to.
Over the past 7 years, lots of spacecraft observations have given us evidence for the presence of water on Mars, either at the surface or not far below. Radar data have shown that large amounts of water ice are stored at the poles (Lots of Pure Water Ice at Mars North Pole). And pictures of gullies have hinted at reserves of water beneath the surface (NASA Says Liquid Water Made Martian Gullies). Now, a team of scientists, led by Dr. William Feldman of the Planetary Science Institute in Tucson, Arizona, have taken a new look at some of that data.
Dr. Feldman and his team used data from the Mars Odyssey Neutron Spectrometer (MONS) to estimate the amount of water ice that is present outside of the polar regions of Mars, where water ice is not expected to be found. The MONS is an instrument that counts Martian neutrons from orbit. These “neutron counts” are sensitive to the presence of hydrogen and how deep it is below the surface. Using models that take the characteristics of the Martian surface and the relationship of hydrogen to water into account, the MONS data can be used to predict the amount and depth of water and water ice in the surface. Doing just that, Dr. Feldman’s team produced a nearly global map of potential underground ice deposits.
New estimates of water ice on Mars suggest there may be large reservoirs of underground ice at non-polar latitudes. The map here shows "water-equivalent hydrogen". Oranges and reds on the map (values greater than 4.5 weight % water-equivalent hydrogen at the surface) point out areas where the amount of deeply buried water ice is greater than what can fit in the pore spaces of the surface rocks. Image credit: Feldman et al., 2011.
This map shows the “weight percent of water-equivalent hydrogen”, or how much of the rock’s weight comes from hydrogen that is bound up in water molecules. Since hydrogen atoms are much lighter than the other atoms that make up a rock, a small weight percent of hydrogen equals a much larger volume of water ice. In fact, Dr. Feldman’s team estimate that values of 4.5 weight % hydrogen or greater (oranges and reds on the map), mean the volume of water ice at depth is larger than what can fit into pore spaces (the spaces between the grains that make up a rock). This means that you no longer have ice in a rock; now you have rocks in ice!
Four regions containing such bulk ice stand out in the map: Promethei Terra in the lower right of the map, Arabia Terra in the upper centre, Arcadia Planitia in the upper left, and Elysium Planetia spanning from the centre right, across the Martian “date line” (180 degrees longitude), to the centre left of the map. The ice deposits here are “buried less than about 1 m below the surface,” writes Dr. Feldman. He does admit that their findings may also indicate the presence of large quantities of minerals that contain water molecules in their chemical make-up. However, their results are supported by other evidence. In the Elysium Planetia region, evidence of glacial features has been seen in high resolution stereo data from ESA’s Mars Express orbiter ( Mars Express Reveals Possible Martian Glaciers). And in the Arcadia Planitia region, buried water ice has been identified in CRISM data, where an almost pure ice layer was excavated from less than 1 meter below the surface by four recent impact events.
Almost pure water ice is seen in the ejecta surrounding this impact crater (8 meters in diameter), which formed in 2008. The only reason we can see ice at the surface here is because this crater is so young. As time passes, the ice will all sublimate away. Image Credit: High Resolution Imaging Science Experiment camera, NASA/JPL-Caltech/University of Arizona.
So, if ice is unstable at today’s conditions on Mars, how can Dr. Feldman and his team account for the presence of that much ice so close to the surface? Well, the bulk ice could have been deposited some 10-20 million years ago, at a time when ice was stable at the surface. If that happened, then the ice sheet could have been preserved under a layer of cemented dust and sediment. This duricrust would have partially shielded the ice from contemporary surface temperatures and atmospheric conditions, slowing the sublimation of the ice just enough so that some of it was left for us to detect today.
Viewing the South Pole of Vesta and Rhea Silvia Impact Basin. This image obtained by Dawn’s framing camera shows the south pole of the giant asteroid Vesta and the circular Rheasilvia impact basin which scientists believe originated by a collision with another asteroid early in the asteroid's history. The image was recorded from a distance of about 1,700 miles (2,700 kilometers). The image resolution is about 260 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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The mysterious asteroid Vesta may well have more surprises in store. Despite past observations that Vesta would be nearly bone dry, newly published research indicates that about half of the giant asteroid is sufficiently cold and dark enough that water ice could theoretically exist below the battered surface.
Scientists working at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland have derived the first models of Vesta’s average global temperatures and illumination by the Sun based on data obtained from the Hubble Space Telescope.
“Near the north and south poles, the conditions appear to be favorable for water ice to exist beneath the surface,” says Timothy Stubbs of NASA’s Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland, Baltimore County. The research by Timothy Stubbs and Yongli Wang, of the Goddard Planetary Heliophysics Institute at the University of Maryland, was published in the January 2012 issue of the journal Icarus.
If any water lurks beneath Vesta, it would most likely exist at least 10 feet (3 meters) below the North and South poles because the models predict that the poles are the coldest regions on the giant asteroid and the equatorial regions are too warm. Global Map of Average Surface Temperature of Vesta
This global map of average surface temperature shows the warmer equatorial zone of the giant asteroid Vesta is likely too warm to sustain water ice below the surface. But roughly half of Vesta is so cold and receives so little sunlight on average that water ice could have survived there for billions of years. The dividing lines (solid gray) are found at about 27 degrees north latitude and 27 degrees south latitude. This map, with temperatures given in kelvins, comes from the first published models of the average global temperature and illumination conditions on Vesta. Credit: NASA/GSFC/UMBC
If proven, the existence of water ice at Vesta would have vast implications for the formation and evolution of the tiny body and upend current theories.
The surface of Vesta is not cold enough for ice to survive all the time because unlike the Moon, it probably does not have any significant permanently shadowed craters where water ice could stay frozen on the surface indefinitely.
Even the huge 300 mile diameter (480-kilometer) crater at the South Pole is not a good candidate for water ice because Vesta is tilted 27 degrees on its axis, a bit more than Earth’s tilt of 23 degrees.
By contrast, the Moon is only tilted 1.5 degrees and possesses many permanently shadowed craters. NASA’s LCROSS impact mission proved that water ice exists inside permanently shadowed lunar craters.
New modeling shows that, under present conditions, Vesta's polar regions are cold enough (less than about 145 kelvins) to sustain water ice for billions of years, as this map of average surface temperature around the asteroid's south pole indicates.
The models predict that the average annual temperature around Vesta’s poles is below minus 200 degrees Fahrenheit (145 kelvins). Water ice is not stable above that temperature in the top 10 feet of Vestan soil, or regolith.
At the equator and in a band stretching to about 27 degrees north and south in latitude, the average annual temperature is about minus 190 degrees Fahrenheit (145 kelvins), which is too high for the ice to survive.
“On average, it’s colder at Vesta’s poles than near its equator, so in that sense, they are good places to sustain water ice,” says Stubbs in a NASA statement. “But they also see sunlight for long periods of time during the summer seasons, which isn’t so good for sustaining ice. So if water ice exists in those regions, it may be buried beneath a relatively deep layer of dry regolith.”
Vesta is the second most massive asteroid in the main Asteroid belt between Mars and Jupiter.
NASA’s Dawn Asteroid Orbiter is the very first mission to Vesta and achieved orbit in July 2011 for a 1 year long mission.
Dawn is currently circling Vesta at its lowest planned orbit. The three science instruments are snapping pictures and the spectrometers are collecting data on the elemental and mineralogical composition of Vesta.
The onboard GRaND spectrometer in particular could shed light on the question of whether water ice exists at Vesta.
So far no water has been detected, but the best data is yet to come.
In July 2012, Dawn fires up its ion thrusters and spirals out of orbit to begin the journey to Ceres, the largest asteroid of them all.
Ceres is believed to harbor huge caches of water, either as ice or in the form of oceans and is a potential habitat for life.
