New Images of the Martian Moons: Phobos and Deimos

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With a fleet of spacecraft orbiting Mars, and rovers crawling across its surface, there’s a flood of images of the Red Planet. It’s nice to know the scientists working on those missions can take the time to look elsewhere every now and then. So today, let me present to you some images of the Martian moons: Phobos and Deimos.

The two images of the Martian moons were captured by the Compact Reconnaissance Imaging Spectrometer for Mars on board NASA’s Mars Reconnaissance Orbiter. Both images were captured while spacecraft was over Mars’ night side, and the ground below was dark.

In order to reorient away from Mars to view the moons, MRO had to turn off its normal nadir-viewing geometry.

The image of Phobos (on the top) was captured on October 23, and shows features as small as 400 metres (1320 feet) across. The image of Deimos was captured on June 7, and shows features as small as 1.3 km (0.8 miles) across.

Phobos is only 21 km (13 miles) across, and orbits Mars once every 7 days, 39 minutes. Because the moon orbits Mars faster than it rotates, Phobos would appear to travel backwards across the sky from an observer on the ground. This is just an illusion, though. Even though it’s tiny, Phobos orbits so closely that it would appear to be 1/3rd the size of our own moon in the sky.

Deimos is even smaller – 12 km (7.5 miles) – but it orbits more distantly than Phobos. It takes 1 day, 6 hours and 17 minutes to orbit the planet. Deimos isn’t large enough that you could make out any features from the surface of Mars. Instead, it would just look like a bright star in the night sky.

The first ever spacecraft observations of the Martian moons were made by Mariner 9 and the Viking Orbiter spacecraft. They found the moons to have very low reflectivity, and appeared to be similar in structure to carbonaceous chondrite meteorites. This led to the commonly held view that the moons are captured asteroids.

Original Source: MRO News Release

Meteorites Reveal Mars’ Past: Molten Surface, Thick Atmosphere

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If Mars ever had water flowing on its surface, as the many canyons and riverbed-like features on the Red Planet seem to indicate, it also would have needed a thicker atmosphere than what encircles that planet today. New research has revealed that Mars did indeed have a thick atmosphere for about 100 million years after the planet was formed. But the only thing flowing on Mars’ surface at that time was an ocean of molten rock.

A study of Martian meteorites found on Earth shows that Mars had a magma ocean for millions of years, which is surprisingly long, according to Qing-Zhu Yin, assistant professor of geology at the University of California- Davis. For such a persistent event, a thick atmosphere had to blanket Mars to allow the planet to cool slowly.

Meteorites called shergottites were studied to document volcanic activities on Mars between 470 million and 165 million years ago. These rocks were later thrown out of Mars’ gravity field by asteroid impacts and delivered to Earth — a free “sample return mission” as the scientists called it — accomplished by nature.

By precisely measuring the ratios of different isotopes of neodymium and samarium, the researchers could measure the age of the meteorites, and then use them to work out what the crust of Mars was like billions of years before that. Previous estimates for how long the surface remained molten ranged from thousands of years to several hundred million years.

The research was conducted by the Lunar and Planetary Institute, UC Davis and the Johnson Space Center.

Planets form by dust and rocks coming together to form planetisimals, and then these small planets collide together to form larger planets. The giant collisions in this final phase would release huge amounts of energy with nowhere to go except back into the new planet. The rock would turn to molten magma and heavy metals would sink to the core of the planet, releasing additional energy. The molten mantle eventually cools to form a solid crust on the surface.

Although Mars appears to no longer be volcanically active, NASA’s Mars Global Surveyor Spacecraft discovered that the Red Planet hasn’t completely cooled since its formation 4.5 billion years ago. Data from MGS in 2003 indicated that Mars’ core is made either of entirely liquid iron, or it has a solid iron center surrounded by molten iron.

Original News Source: UC Davis Press Release

Ancient Salt Deposits in a Martian Crater

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Here’s an interesting image released today captured by NASA’s Mars Reconnaissance Orbiter. It’s of an unnamed crater on Mars in the Terra Cimmeria region that could contain ancient deposits of chloride salts. The region is one of the most geologically interesting on Mars. It’s riddled with impact craters, crisscrossed by dried up river channels, and sculpted by wind. Water probably acted on the region a long time ago, building up the salt deposits.

This region of Mars is of great interest to scientists. Three separate missions have studied the area in great detail: Mars Global Surveyor, Mars Odyssey, and now the Mars Reconnaissance Orbiter. Over the years, they have shown how these small deposits of chloride salts are scattered across the Martian surface.

They’re more widely found in the Noachian (most ancient) regions, and less found in the Hesperian (middle geologic time) terrain. This means that the deposits were probably laid down in the earliest epochs of Martian history, and then later geologic processes resurfaced them.

This image, captured by the HiRISE instrument on NASA’s Mars Reconnaissance Orbiter shows one of these deposits. The photograph reveals an area about 900 metres across, including a partially buried unnamed crater in Terra Cimmeria. The chloride salt deposits in this photograph are the lighter toned colour. The deposits are relatively thin and occur in low lying areas. This one has been heavily eroded, which suggests that it’s very old.

Original Source: HiRISE News Release

Mars Rovers’ Mission Extended Yet Again

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NASA originally expected they’d only last a few months, but the plucky Martian rovers are still crawling across the surface of Mars – more than 3 years later. So the agency has gone ahead and extended their missions… again. This is the fifth time NASA has extended their mission, keeping them operational potentially through 2009.

The twin rovers landed on the surface of Mars in January, 2004. Mission planners expected that it would only take a few months before dust coated the rovers’ solar panels so thickly that they wouldn’t be able to generate power any more. But the Martian weather had a trick; dust devils and wind gusts came by often enough to keep the solar panels relatively clear of dust. Without the loss of power looming, the rovers have been able to keep going, and going, and going.

Their accomplishments to date have been staggering. So far, Spirit has driven a total of 7.26 kilometers (4.51 miles) and has returned more than 102,000 images. Opportunity has driven 11.57 kilometers (7.19 miles) and has returned more than 94,000 images.

Opportunity turned up evidence of the planet’s watery past, when oceans affected rocks for long periods of time, and deposited layers of material. Spirit also found that water altered the mineral composition of the rocks and soil in its surroundings. The rovers have been instrumental in helping scientists understand the Martian dust devils. And both have discovered metallic meteorites sitting the surface of the Red Planet. One of these has a similar composition to the meteorite that reached Earth from Mars.

Original Source: NASA/JPL News Release

Maunder Crater on Mars

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Seen one Martian crater and you’ve seen them all right? Well, check this one out. It’s an image of Maunder Crater on the surface of Mars, captured by ESA’s Mars Express. Although the crater is large, 90 km (56 miles) across, it’s very shallow – less than a kilometre. It used to be much deeper, but some geologic process has since filled it in.

The images of Maunder crater were captured in late 2005 by Mars Express at a resolution of roughly 15 metres per pixel. The crater, named after British astronomer Edward W. Maunder, is located about halfway between Argyre Planitia and Hellas Planitia on the southern Highlands of Mars.

It once looked like a more traditional crater, but then something happened on the west side to make it cave in. A large landslide pushed material from the crater wall to the inner portion. The edges of the crater that remain show gullies that could have been created when large amounts of material was flowing down into the crater.

One intriguing discovery: there are gullies along the upper side of the trough in the middle of the crater that have been caused by seeping water.

Original Source: ESA News Release

High Resolution Views of Potential Mars Landing Sites

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Mission planners for the Mars Science Laboratory have quite a challenge on their hands. Where should they land the rover in 2010? They’ve got a whole planet to choose from. Well, they’ve narrowed the field of prospective landing sites down to about 30 intriguing candidates. And now NASA’s Mars Reconnaissance Orbiter has delivered high resolution images of each and every potential landing site… in colour!

We’ve got Spirit and Opportunity currently crawling across the surface of Mars. The Phoenix Mars Lander is on its way now. But when NASA’s Mars Science Laboratory arrives in 2010, the science is really going to get rolling. This SUV-sized robotic explorer will bring its own nuclear power source, and a suite of science instruments, giving it the range and capabilities to find life on the surface of the Red Planet.

But where should it land? The University of Arizona’s HiRISE team delivered 143 images captured by NASA’s Mars Reconnaissance Orbiter to the researchers this week, showcasing each location in false and enhanced colour.

Normally the spacecraft captures its images in black-and-white. It’s relatively simple to grab a single image of the Martian surface with one of its filters. When you’re trying to get colour, though, things become more complicated. The spacecraft moves so quickly above Mars that it’s very difficult to capture several images of the same area in different wavelengths of light and then merge them together into a single colour image.

Researchers with the HiRISE team have developed a computer program that can process data from different colour filters and merge them into a single image. Of course, to process each 20,000 by 50,000 pixel region can take several hours.

Mission planners for the Mars Science Laboratory will be meeting at a workshop later this month to try and narrow down the field of choices. These colour photographs will help them make a decision.

You can browse all the images yourself if you like. Click here to see them. You can also access the movie that pans across a potential landing site at Nili Fossae. The animation shows a range of enhanced colours that reveal rocks that might have been altered by water in the past.

Original Source: UA News Release

True or False (Color): The Art of Extraterrestrial Photography

Carina Nebula. Image credit: Hubble Space Telescope/NASA.

When you look at the amazing pictures captured by the Hubble Space Telescope, or the Mars Exploration Rovers, do you ever wonder: is that what you’d really see with your own eyes? The answer, sadly, is probably not. In some cases, such as with the Mars rovers, scientists try and calibrate the rovers to see in “true color,” but mostly, colors are chosen to yield the most science. Here’s how scientists calibrate their amazing instruments, and the difference between true and false colors.

So, to start off, let’s put this in the form of a true or false question: T or F: When we see the gorgeous, iconic images from Hubble or the stunning panoramas from the Mars rovers, do those pictures represent what human eyes would see if they observed those vistas first hand?

Answer: For the Hubble, mostly false. For the rovers, mostly true, as the rovers provide a combination of so-called “true” and “false” color images. But, it turns out, the term “true color” is a bit controversial, and many involved in the field of extraterrestrial imaging are not very fond of it.

“We actually try to avoid the term ‘true color’ because nobody really knows precisely what the ‘truth’ is on Mars,” said Jim Bell, the lead scientist for the Pancam color imaging system on the Mars Exploration Rovers (MER). In fact, Bell pointed out, on Mars, as well as Earth, color changes all the time: whether it’s cloudy or clear, the sun is high or low, or if there are variations in how much dust is in the atmosphere. “Colors change from moment to moment. It’s a dynamic thing. We try not to draw the line that hard by saying ‘this is the truth!'”

Bell likes to use the term “approximate true color” because the MER panoramic camera images are estimates of what humans would see if they were on Mars. Other colleagues, Bell said, use “natural color.”

Zolt Levay of the Space Telescope Science Institute produces images from the Hubble Space Telescope. For the prepared Hubble images, Levay prefers the term “representative color.”

“The colors in Hubble images are neither ‘true’ colors nor ‘false’ colors, but usually are representative of the physical processes underlying the subjects of the images,” he said. “They are a way to represent in a single image as much information as possible that’s available in the data.”

True color would be an attempt to reproduce visually accurate color. False color, on the other hand, is an arbitrary selection of colors to represent some characteristic in the image, such as chemical composition, velocity, or distance. Additionally, by definition, any infrared or ultraviolet image would need to be represented with “false color” since those wavelengths are invisible to humans.

The cameras on Hubble and MER do not take color pictures, however. Color images from both spacecraft are assembled from separate black & white images taken through color filters. For one image, the spacecraft have to take three pictures, usually through a red, a green, and a blue filter and then each of those photos gets downlinked to Earth. They are then combined with software into a color image. This happens automatically inside off-the-shelf color cameras that we use here on Earth. But the MER Pancams have 8 different color filters while Hubble has almost 40, ranging from ultraviolet (“bluer” than our eyes can see,) through the visible spectrum, to infrared (“redder” than what is visible to humans.) This gives the imaging teams infinitely more flexibility and sometimes, artistic license. Depending on which filters are used, the color can be closer or farther from “reality.”

Stone mountain rock outcrop in true and false colour. Image credit: NASA/JPL
Stone mountain rock outcrop in true and false colour. Image credit: NASA/JPL

The same rock imaged in true and false color by Opportunity.

In the case of the Hubble, Levay explained, the images are further adjusted to boost contrast and tweak colors and brightness to emphasize certain features of the image or to make a more pleasing picture.

But when the MER Pancam team wants to produce an image that shows what a human standing on Mars would see, how do they get the right colors? The rovers both have a tool on board known as the MarsDial which has been used as an educational project about sundials. “But its real job is a calibration target,” said Bell. “It has grayscale rings on it with color chips in the corners. We measured them very accurately and took pictures of them before launch and so we know what the colors and different shades of grey are.”

One of the first pictures taken by the rovers was of the MarsDial. “We take a picture of the MarsDial and calibrate it and process it through our software,” said Bell. “If it comes out looking like we know it should, then we have great confidence in our ability to point the camera somewhere else, take a picture, do the same process and that those colors will be right, too.”

Hubble can also produce color-calibrated images. Its “UniverseDial” would be standard stars and lamps within the cameras whose brightness and color are known very accurately. However, Hubble’s mission is not to produce images that faithfully reproduce colors. “For one thing that is somewhat meaningless in the case of most of the images,” said Levay, “since we generally couldn’t see these objects anyway because they are so faint, and our eyes react differently to colors of very faint light.” But the most important goal of Hubble is produce images that convey as much scientific information as possible.

The rover Pancams do this as well. “It turns out there is a whole variety of iron-bearing minerals that have different color response at infrared wavelengths that the camera is sensitive to,” said Bell, “so we can make very garish, kind of Andy Warhol-like false color pictures.” Bell added that these images serve double duty in that they provide scientific information, plus the public really enjoys the images.

And so, in both Hubble and MER, color is used as a tool, to either enhance an object’s detail or to visualize what otherwise could not be seen by the human eye. Without false color, our eyes would never see (and we would never know) what ionized gases make up a nebula, for example, or what iron-bearing minerals lie on the surface of Mars.

As for “true color,” there’s a large academic and scholarly community that studies color in areas such as the paint industry that sometimes gets upset when the term “true color” is used by the astronomical imaging group, Bell explained.

“They have a well-established framework for what is true color, and how they quantify color,” he said. “But we’re not really working within that framework at that level. So we try to steer away from using the term ‘true color’.”

Levay noted that no color reproduction can be 100% accurate because of differences in technology between film and digital photography, printing techniques, or even different settings on a computer screen. Additionally, there are variations in how different people perceive color.

“What we’re doing on Mars is really just an estimate,” Bell said, “it’s our best guess using our knowledge of the cameras with the calibration target. But whether it is absolutely 100% true, I think it’s going to take people going there to find that out.”

For more information see http://hubblesite.org/ or check out Jim Bell’s 2006 book “Postcards From Mars.”

Opportunity is Now Working Inside Victoria Crater

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When last we saw our plucky rover, it was tentatively crawling down into the massive Victoria crater on the surface of Mars. Well, NASA’s Mars Opportunity rover has been making some serious progress since then. In fact, it’s already gotten down to do some science. The rover is currently several metres down inside the rim of Victoria crater, balancing on a steep slope, and peering at an ancient slab of exposed bedrock.

Opportunity is now slowly descending down into the 800-metre-wide Victoria Crater; slowly, and carefully. Its first stop is a patch of exposed bedrock. Even though it’s still on the slope, Opportunity was able to reach over with its robotic arm and use some of its tools to examine the bright outcropping.

Controllers had Opportunity make a few extra safety checks, since it’s currently driving down a 25-degree slope, and stretching out the arm too far could unbalance it. The rover drove down 2.25 metres (7.38 feet) to get the rock within easy – and safe – reach. This was the third drive the rover has made since it entered the crater on September 13th.

NASA is watching the rover’s traction very carefully. This 25-degree angle is the steepest the rover is going to see. And so far, the worst slippage has only been about 10%. So it should be able to get down into the crater, and still be able to crawl back out again. Fortunately, Victoria crater won’t be Opportunity’s final home on Mars.

Researchers are hoping the rover will find older and older patches of rock, exposed when an asteroid impacted the surface of Mars millions of years ago. These ancient rocks will tell a story of Martian history much older than the fragmented pieces scientists have been able to put together so far. Were there long periods where the planet was covered by liquid water?

It’s your job Opportunity. Don’t come out of your hole until you’ve got some answers.

Original Source: NASA/JPL News Release

These are Tough Microbes, But They Don’t Come from Mars

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You know the cliche, wherever we find water here on Earth, we find life. But what if the environment is really hostile? So hostile that any living creature would almost never see water. And even when there was water, they were constantly being blasted with radiation. Amazingly, there’s a microbe out there, Deinococcus geothermalis, that can handle some of the harshest environments on the planet – favoured habitats include nuclear power plants. Scientists once suspected that microbes like this might have evolved on Mars. Nope, they’re homegrown.

Of all the different strains of bacteria on Earth, those in the genus Deinococcus are a hardy bunch. They’re extremely resistant to ionizing radiation, they laugh at ultraviolet light, extreme, heat, cold and they don’t mind being completely dried out for long periods. Bathed in acid? Boring.

D. geothermalis is actually a cousin of another microbe called Deinococcus radiodurans. D. radiodurans is capable of withstanding 500 times the radiation that will kill a human – with no loss of viability. The Guiness Book of World records calls D. radiodurans the toughest bacteria in the world, and some scientists have proposed that it actually evolved on Mars and somehow journeyed to Earth.

Researchers have recently sequenced the bacteria’s cousin, D. geothermalis’ entire genome sequence, providing some valuable clues into how a microbe can be so tough, and how they two are related (no Martian explanation necessary).

Their paper describing the results of their sequencing efforts, entitled Deinococcus geothermalis: The Pool of Extreme Radiation Resistance Genes Shrinks will be published in the September 26th issue of the journal Public Library of Science.

The microbe was first discovered in a hot pool at the Termi di Agnano, in Naples, Italy. Other scientists have turned it up in other nasty locations, such as industrial paper machine water, deep ocean subsurface environments, and subterranean hot springs in Iceland.

While working with the microbe, the researchers noted, “the extraordinary survival of Deinococcus bacteria following irradiation has also given rise to some rather whimsical descriptions of their derivation, including that they evolved on Mars.”

In fact, the US Department of Energy is considering D. geothermalis as a possible solution to break down radioactive waste. Which would be good, since it’s often a pest; adhering to the surface of steel, and causing problems in nuclear power plants.

Currently, scientists have no idea why bacteria like D. geothermalis are so hardy to radiation. They’re just as susceptible to normal bacteria to have their DNA broken up by radiation, but they use some kind of efficient repair mechanism to fix the damage quickly.

The big surprise with this research is that it overturns previously held theories about how D. radiodurans protects itself. The two strains of bacteria are both extremely resistant to radiation, and yet D. geothermalis lacks the genes that scientists thought D. radiodurans was using. By comparing genome sequences between the two strains, the researchers were able to narrow down the genes which are likely contributing to the microbes’ tolerance.

This research also overturns the intriguing possibility that D. radiodurans comes from Mars; evolving on the Cosmic Ray blasted surface of the Red Planet. These two strains have enough in common, with traceable evolutionary steps, that the researchers can see how they evolved right here on Earth.

Here’s Dr. Michael J. Daly, an associate professor at the Uniformed Services University of the Health Sciences in Bethesda, “the thermophile Deinococcus geothermalis is an excellent organism in which to consider the potential for survival and biological evolution beyond its planet of origin, as well as the ability of life to survive extremely long periods of metabolic dormancy in high-radiation environments. The current work reinforces the notion that resistance to radiation and desiccation readily evolved on Earth, and that the underlying resistance systems are based on a universal set of repair genes. The work underscores the vulnerability of potential life-inhabiting environments on Mars to contamination by human exploration; and how the efficiency of ordinary DNA repair proteins could be increased, which might be important to astronauts. The growing awareness that there is hardly a habitat on Earth not harboring life is now changing our consensus of consequences for possible life on Mars.”

Sorry Mars, go evolve your own microbes.

Original Source: PLOS Journal article

More Martian Cave Entrances Discovered

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More Mars news… NASA’s Mars Odyssey spacecraft has turned up what look like the entrances to caves along the slope of a Martian volcano. If these turn out to be actual tunnels or caves, they could be a scientific goldmine, offering future explorers protection and a unique region to study – perhaps even life could be hiding away from hostile Martian surface environment.

The seven possible cave entrances are dark, and nearly circular, ranging in size from 100 to 250 metres (328 to 820 feet) across. They were discovered by NASA’s Mars Odyssey and Mars Global Surveyor spacecraft. Follow up observations with Odyssey’s infrared cameras confirmed that they could very well be cavernous entrances into underground regions on Mars.

The infrared evidence showed that the temperatures inside the holes changed less than the surrounding regions. “They are cooler than the surrounding surface in the day and warmer at night,” said Glen Cushing of the U.S. Geological Survey’s Astrogeology Team and of Northern Arizona University, Flagstaff, Ariz. “Their thermal behavior is not as steady as large caves on Earth that often maintain a fairly constant temperature, but it is consistent with these being deep holes in the ground.”

One of the downsides of these caves is their altitude. They’re located near the top of a massive Martian volcano called Arsia Mons. At this high altitude, life would have a difficult time coping with the extreme cold and lower air pressure.

Planetary geologists think the caves might have been formed by underground stresses around the volcano. The caves are inline with with other bowl-shaped pits that appear to have been formed when material collapsed. There could be long networks of tunnels and stress fractures. In some cases, the roof just collapsed in completely, and in other places, you might get a cave entrance instead.

The next step is to bring the much more powerful Mars Reconnaissance Orbiter’s camera in to image the regions better. It might be able to shed some light on the mystery.

Original Source: NASA/JPL News Release