Category: Mars

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Dust — a solar panel’s worst nightmare.

Is sending solar-powered robots to the Red Planet a bad idea? Mars is a very dusty planet, and Mars dust sticks to everything, especially solar arrays. After all, Phoenix’s death was probably hastened by a Sun-blocking dust storm, and rover Spirit was battered by the combined solar panel-coated dust layer plus dust storm, nearly draining its batteries (as can be seen in the comparison above, after two years on the Martian surface, Spirit’s dusty layer was already an acute problem).

However, a NASA-sponsored MIT think-tank has weighed up the future energy needs of a manned settlement on Mars and arrived at an interesting conclusion…

It sounds like the “nuclear space debate” continues. Thinking back to when Galileo was launched toward Jupiter in 1989, or when Cassini was sent to Saturn in 1997, huge protests erupted from critics, Cape Canaveral neighbours and anti-nuclear organizations. The argument was that should there be a launch accident, the radioactive material contained inside the radioisotope thermal generators (RTGs) could be scattered through the atmosphere and over a wide area on the ground (i.e. death and destruction). While this is a scary thought, NASA engineers were very quick to point out that RTGs are virtually indestructible, even under extreme conditions during an explosion and atmospheric re-entry.

The motivation for sending plutonium (non-weapon grade Pu238) on board missions to Jupiter and Saturn has even been called into question, spawning wild conspiracy theories such as “Project Lucifer.” Therefore, it seems only sensible that NASA should want to carry out an in-depth study of all energy production techniques before committing to a potentially unpopular (and therefore politically damaging) nuclear source for future Mars colonies.

With the help of energy specialists from the Massachusetts Institute of Technology (MIT), NASA commissioned a study of how future manned Mars settlements can be powered. Will nuclear generators need to be constructed? Or can solar panels fulfil our proto-colony’s energy needs (regardless of the dust situation)?

Interestingly, if positioned in the correct location, solar arrays might function just as well, if not better, than the nuclear options. Solar panels could provide all the energy a fledgling colony needs.

The MIT researchers assessed 13 different energy generation systems and compared solar and nuclear options. In a presentation last month at the International Astronautical Congress in Glasgow, MIT engineer Wilfried Hofstetter compared nuclear fission reactors, RTGs, Sun-tracking solar panel arrays and non-tracking thin-film solar arrays laid atop the Martian landscape.

Like any space travel endeavour, efficiency is paramount; astronauts will need to utilize every last energy-generating ounce of equipment sent to Mars (including back-up systems).

It would appear that a large solar panel array can match nuclear generators, only if they are situated at a latitude of 0-40° north of the Martian equator. Southern latitudes have much less solar energy available for most of the year.

So what’s the best plan of action? According to Hofstetter, a Mars mission should be able to transport several 2 metre-wide rolls of thin-film solar panel arrays. Rolling out an array of these thin-film rolls could supply ample energy to a colony. For example, if the array is positioned at 25° north, measuring 100×100 metres, 100 kilowatts can be generated. The MIT researchers even calculated it would take two astronauts 17 hours to construct the array (alternatively they could get a robot to do it).

Commenting on this Mars energy solution, Colin Pillinger, planetary scientist with the Open University, UK (and head Beagle 2 scientist) said the solar array’s old foe — dust — shouldn’t be too much of a problem after all. “Dust storms tend to start in well-known places in the southern hemisphere as it warms up, so it shouldn’t be too difficult to avoid them,” he said.

So the skies may be clear for solar energy on Mars after all. Even though dust storms causes problems for our robotic explorers, manned expeditions may be able to avoid them all together. Besides, I don’t see why astronauts couldn’t pack some brushes to wipe down the arrays should dust become a problem…

Source: New Scientist

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There’s more than just a little ice under Mars’ surface. According to data from the Mars Reconnaissance Orbiter radar system, vast Martian glaciers of water ice lie buried under rocky debris. And this ice is not just at the Arctic region where the Phoenix lander scratched the surface in searching for ice. MRO found evidence for a huge amount of underground ice at much lower latitudes than any ice previously identified on the Red Planet. “Altogether, these glaciers almost certainly represent the largest reservoir of water ice on Mars that is not in the polar caps,” said John W. Holt of the University of Texas at Austin, who is lead author of the report. “Just one of the features we examined is three times larger than the city of Los Angeles and up to half a mile thick. And there are many more. In addition to their scientific value, they could be a source of water to support future exploration of Mars.”

Scientists say buried glaciers extend for dozens of miles from the edges of mountains or cliffs. A layer of rocky debris blanketing the ice may have preserved the underground glaciers as remnants from an ice sheet that covered middle latitudes during a past ice age. This discovery is similar to massive ice glaciers that have been detected under rocky coverings in Antarctica.

Scientists have been puzzled by what are known as aprons — gently sloping areas containing rocky deposits at the bases of taller geographical features — since NASA’s Viking orbiters first observed them on the Martian surface in the1970s. One theory has been that the aprons are flows of rocky debris lubricated by a small amount ice. Now, the shallow radar instrument on the Mars Reconnaissance Orbiter has provided scientists an answer to this Martian puzzle.

“These results are the smoking gun pointing to the presence of large amounts of water ice at these latitudes,” said Ali Safaeinili, a shallow radar instruments team member with NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

The buried glaciers lie in the Hellas Basin region of Mars’ southern hemisphere. The radar also has detected similar-appearing aprons extending from cliffs in the northern hemisphere.

Radar echoes received by the spacecraft indicated radio waves pass through the aprons and reflect off a deeper surface below without significant loss in strength. That is expected if the apron areas are composed of thick ice under a relatively thin covering. The radar does not detect reflections from the interior of these deposits as would occur if they contained significant rock debris. The apparent velocity of radio waves passing through the apron is consistent with a composition of water ice.

“There’s an even larger volume of water ice in the northern deposits,” said JPL geologist Jeffrey J. Plaut, who will be publishing results about these deposits in the American Geophysical Union’s Geophysical Research Letters. “The fact these features are in the same latitude bands, about 35 to 60 degrees in both hemispheres, points to a climate-driven mechanism for explaining how they got there.”

The rocky debris blanket topping the glaciers apparently has protected the ice from vaporizing, which would happen if it were exposed to the atmosphere at these latitudes.

“A key question is, how did the ice get there in the first place?” said James W. Head of Brown University in Providence, R.I. “The tilt of Mars’ spin axis sometimes gets much greater than it is now. Climate modeling tells us ice sheets could cover mid-latitude regions of Mars during those high-tilt periods. The buried glaciers make sense as preserved fragments from an ice age millions of years ago. On Earth, such buried glacial ice in Antarctica preserves the record of traces of ancient organisms and past climate history.”

Source: NASA

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Data from the Mars Odyssey orbiter’s Gamma Ray Spectrometer provides new evidence for the controversial idea that oceans once covered about a third of ancient Mars. Spacecraft images going back to Mariner 9 in the early 1970s and the Viking orbiters and landers later in the 1970s up to the current orbiters and rovers have showed widespread evidence for a watery past for Mars. About 20 years ago, several studies sparked a scientific debate on the possible existence of ancient Martian oceans marked by visible shorelines. Images and topographic maps provide evidence for two different oceans in one area, perhaps occuring at different times in Mars history, a larger one at an earlier time, and a smaller once existing later. Odyssey’s GRS can detect subsurface elements, and new data confirms the right combination of elements for two ancient shorelines.

The spectrometer has the unique ability to detect elements buried as much as 1/3 meter, or 13 inches, below the surface by the gamma rays they emit. That capability led to GRS’ 2002 discovery of water-ice near the surface near Mars arctic region, leading to the decision for the Phoenix landing site.

“Our investigation posed the question, ‘Might we see a greater concentration of these elements within the ancient shorelines because water and rock containing the elements moved from the highlands to the lowlands, where they eventually ponded as large water bodies?'” said University of Arizona planetary geologist James M. Dohm, who led the international investigation. “We compared Gamma Ray Spectrometer data on potassium, thorium and iron above and below a shoreline believed to mark an ancient ocean that covered a third of Mars’ surface, and an inner shoreline believed to mark a younger, smaller ocean.”

Results suggest that past watery conditions likely leached, transported and concentrated such elements as potassium, thorium and iron, Dohm said. “The regions below and above the two shoreline boundaries are like cookie cutouts that can be compared to the regions above the boundaries, as well as the total region.”

The younger, inner shoreline is evidence that an ocean about 10 times the size of the Mediterranean Sea, or about the size of North America, existed on the northern plains of Mars a few billion years ago. The larger, more ancient shoreline that covered a third of Mars held an ocean about 20 times the size of the Mediterranean, the researchers estimate.

The potassium-thorium-iron enriched areas occur below the older and younger paleo-ocean boundaries with respect to the entire region, they said. The scientists used data from Mars Global Surveyor’s laser altimeter for topographic maps of the regions in their study.

Scientists studying spacecraft images have a hard time confirming “shoreline” landforms, the researchers said, because Mars shorelines would look different from Earth’s shorelines. Earth’s coastal shorelines are largely a direct result of powerful tides caused by gravitational interaction between Earth and the moon, but Mars lacks a sizable moon. Another difference is that lakes or seas on Mars could have formed largely from giant debris flows and liquefied sediments. Still another difference is that Mars oceans may have been ice-covered, which would prevent wave action.

“The GRS adds key information to the long-standing oceans-on-Mars controversy,” Dohm said. “But the debate is likely to continue well into the future, perhaps even when scientists can finally walk the Martian surface with instruments in hand, with a network of smarter spaceborne, airborne and ground-based robotic systems in their midst.”

Source: U of Arizona

[/caption]Last week, Mars Exploration Rover Spirit looked as if its sols were numbered. Hot on the heals of the demise of the frozen Phoenix lander, Spirit was about to succumb to a low-energy death brought on by a dust storm. The build-up of dust on the rover’s solar panels were already causing a serious problem, but as a storm raged over Gusev Crater, power output from the panels slumped to an all-time low. As Nancy reported on November 11th, mission controllers were forced to switch Spirit into a low-energy state, leaving them with no other choice but to command the robot to be silent. Although tensions were high, Spirit broke the silence last Thursday.

Now NASA controllers are working hard to manage Spirit’s power production, hopefully extending the life of the highly successful rover longer still…

At its worst, Spirit’s solar panels were outputting 89 watt hours of energy just before NASA mission control took decisive action by shutting down non-essential heaters on the rover. Before the storm, Spirit was already covered in a thick layer of dust from nearly five years of Mars roving, allowing only 33% of the sunlight falling on the panels to be used by the photovoltaic cells. During the storm, the dust situation had worsened, valuable sunlight was getting blocked by atmospheric dust clouds. Spirit was in trouble.

“Spirit is not out of the woods yet,” said Mars Exploration Rover (MER) Project Manager John Callas at NASA’s Jet Propulsion Laboratory. “The storm and all its dust have not gone away completely. And this is the time of the Martian year when storms like this can occur. So the plan ahead is to stay cautious with the rover and work on recharging the batteries while waiting out the rest of the storm’s activity.”

So, Spirit has been put on a low energy consumption diet. On Friday commands were sent to the rover to keep some of its heaters switched off and to conduct limited observations and communications. Spirit will be on a “go-slow” until the end of the month to give it some time to recover, recharge and be prepared in the event of a follow-up Gusev Crater storm.

At the end of the month no commands will be sent from Earth for a period of two weeks, as the Sun will be blocking the line of sight with Mars. Therefore Spirit will have lots of time to recover from the dust storm ordeal until communications between Earth and Mars return. After this period, NASA plans to move Spirit from its current location inside Gusev Crater (a low platform called “Home Plate”) so it can continue to explore the Red Planet (assuming there are no more damaging storms ahead).

Although this is all a huge relief, I can’t help but think that Spirit is on borrowed time.

Source: NASA

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If you watched the “Five Years on Mars” documentary on the National Geographic channel about the Mars Exploration Rovers, you probably saw how both rovers have gotten stuck in some of the small sand dunes on Mars surface. These dune fields on Mars are a bit of a mystery to planetary geologists, and in fact, there is nothing like them on Earth. The fields of rippled sand on Mars, called Transverse Aeolian Ridges (TARs), are found over large areas across Mars. The dunes themselves are smaller than the gigantic dunes also found on Mars, but the fields are bigger than any sand ripple fields found on Earth. TARs hold clues to past and present climate processes, and since they can be death traps for rovers, scientists want to know more about these unusual features.

TARS are formed by the wind. If you frequently peruse the website for the HiRISE Camera on the Mars Reconnaissance Orbiter, you’ll see the word “aeolian” quite often in science themes and descriptions. Aeolian refers to any phenomena involving air movement.

In 2005, the Opportunity rover got stuck in a small dune, called Purgatory Dune for six weeks with its wheels firmly mired in what planetary geologists believe was a small TAR. After the rover was finally freed, from images the rover took of the surrounding area, mission scientists noticed they were surrounded by dunes. (See this link for movies of the rover wheels turning in the sand.) They had to carefully drive around all the dunes, which slowed the progress down considerably. So it’s important to know where TARs are located to avoid landing among them on future rover missions.

One of the people studying TARs is Matt Balme, a research scientist with the the Planetary Science Institute. Balme and his colleagues have conducted a pole-to-pole planet survey of more than 10,000 images taken by the Mars Orbiter Camera, which was (is) on board the Mars Global Surveyor spacecraft.

Here’s what they found about TARs:

-They are more common in the southern hemisphere than in the northern.

-They are found in an equatorial belt between 30 degrees north and 30 degrees south latitude.

-They exist in two distinct environments: near layered terrain or adjacent to Large Dark Dunes (LLDs). Those adjacent to dunes have formed recently, while those near layered terrain are millions of years old.

-They are abundant in the Meridiani Planum region and in southern-latitude craters.

The Opportunity rover’s TAR encounter provided additional data, showing that at least that TAR was composed of an outer layer of granule-sized material ranging from about 2mm to 5 mm in diameter, Balme said. Beneath this was a mixed mass of fine and coarse particles.

“My theory is that the very young TARs are found near the Large Dark Dunes, which are also very young, because the sand blowing off the dunes provides the energy needed to form TARs,” Balme said. “Meanwhile you have areas near layered landforms that used to have active sediment transport, but no longer. This shows a dynamic environment that has changed, and we might be able to use TARs as paleo markers to help decipher ancient climates.”

Current Martian circulation models don’t provide much evidence that wind patterns and atmospheric densities on Mars were significantly different in the past than from what they are today. “But I think the geology we are seeing suggests that there might have been different patterns and densities,” Balme said. “The observations we’re getting now from Mars Global Surveyor and the HiRISE camera are giving us really good data to drive the models.”

Although Blame and his team have discovered much about TARs, they still don’t know what materials compose the various TAR fields or why they’re seeing these large features on Mars but not on Earth.

“Over the next couple of years we should be seeing many more images from HiRISE that can give us more information, for example, about the heights versus spacing and whether TARs have more in common with dunes or the ripple fields found on Earth,” Balme said. “And they could provide insights into present and past climate patterns as we learn more about them and use that data to help drive general circulation models.”

Source: Planetary Science Institute