Martian Southern Cap is Mostly Water Ice

2007-0921southpole.thumbnail.jpg

I’ll warn you right now, it’s raining Mars news today. Take cover. First up, we’ve got this interesting story. Planetary scientists at MIT have estimated that Mars’ southern pole contains the largest quantity of frozen water in the inner solar system (apart from the Earth, of course). Many people believed that frozen carbon dioxide was the predominant substance in the south pole’s cap, but nope, it’s water.

The research was led by Maria Zuber, MIT professor of geophysics, and the lead investigator for gravity for the Mars Reconnaissance Orbiter. The project is funded by the NASA Mars Program.

Scientists have long suspected that the Martian southern pole was mostly ice and dust, covered by a thin coating of carbon dioxide, but they didn’t have a firm estimate. Zuber and her colleagues used topographical and gravitational data by three Mars spacecraft to find the volume and mass of the ice cap.

Once they had the volume and mass, they were able to calculate the density. The density of water ice is 1,000 kg per cubic metre, while the density of solid carbon dioxide (aka dry ice) is 1,600 kg per cubic metre. Their estimates calculated that the Martian southern pole is about 1,220 kg per cubic metre. That indicates that it’s mostly water, with about 15% silicate dust mixed in.

This makes the southern polar region of Mars the largest body of water in the inner solar system, outside of the Earth. Just in case that’s not clear, we’re talking about Mercury, Venus and Mars.

One thing that’s still puzzling astronomers is the fact that the polar cap doesn’t reflect as much as you would expect from a coating of ice. It’s believed that the silicate dust mixed in dulls down the cap’s reflectivity.

Zuber and her team are planning to estimate the northern polar cap.

Original Source: MIT News Release

Mars Has Had Many, Many Ice Ages

2007-0912marsice.thumbnail.jpg

The polar ice caps on Mars have been there for a long time; although, they haven’t always stayed the same size, or shape. They cover the surface between the poles and approximately 60° latitude today, but Norbert Schorghofer of the Institute for Astronomy and NASA Astrobiology Institute in Hawaii has shown that Mars has had at least forty major ice ages during the past five million years.

The Martian ice caps are divided into three layers: a massive bottom sheet, a porous middle layer and a thin, dry, dusty top layer. The makeup and extent of the ice coverage has varied over its long history due to both precipitation of water vapor from the atmosphere, and the diffusion and condensation of water from pores in the ice.

“Although neither of the two mechanisms by itself could simultaneously account for the mass fraction and latitudinal boundary of the observed ice, their combination provides just enough ice at the right places,” Schorghofer said.

Unlike the Earth, Mars doesn’t have a Moon to keep its tilt in check. Instead, the planet is able to tilt as much as 10-degrees from its current angle. This can create tremendous variation in the size of its ice sheets.

Earlier studies of the ice showed that the shifting of the ice was due largely to Mars’ varying tilt (obliquity), and thus changes in global and local temperatures affecting the humidity levels of the entire planet. Schorghofer used computer modeling that takes into account thermal and atmospheric conditions, as well as the growth and retreat of the ice sheets. His research shows that the transfer of water vapor from the ice into the atmosphere, and the condensation of this water back into the ice profoundly altered the way in which the ice caps melted and re-froze.

Closer to the poles, the amount of ice changes very little over time. But near the edges of the sheets, the volume of ice has varied by as much as 100,000 cubic km during each ice age. Mars’ icy love handles have each also shrunk an overall depth of 60cm over the past 2.5 million years.

Understanding the cause for ice ages on Mars may help us learn more about the climate history of other planets, including Earth.

“The dynamic nature of the ice sheets makes Mars an ideal system in which to test and expand our knowledge of astronomical climate forcing. A great deal could be learned about terrestrial ice ages from the study of Martian ice stratigraphy – a longer, cleaner and simpler record than Earth’s,” Schorghofer said.

When the Phoenix Mars Lander arrives at the Red Planet in 2008, it might just see the different kinds of ice layers that Schorghofer is predicting.

Original Source: IfA

Opportunity is Entering Victoria Crater

2007-0912rover.thumbnail.jpg

With the powerful Martian dust storms dissipating, the Mars Exploration Rovers are ready to resume their duties, apparently no worse for wear. When we last met our heroes, Opportunity was about to climb down into Victoria Crater to look for evidence of ancient water. Now it took its first tentative steps into the crater, putting all six wheels onto the slope. And then it crawled back out again. Easy does it…

Victoria Crater measures 800 metres (half a mile) across, and it’s the largest impact crater either of the rovers have encountered during their travels on Mars. Since the crater cuts down through Martian rock, it gives scientists an unprecedented opportunity to peer back in time, when layers of rock were put down – ideally when there was liquid water present.

The rover team commanded Opportunity to drive just far enough on September 11, 2007 that all six of its wheels got onto the inner slope. The rover was then asked to come back out again, so the team could measure the amount that its wheels slipped on the slope. Right at the end, as Opportunity was just crawling out, its wheels slipped further than the rover team wanted, so they had it stop, with its front wheels still on the slope.

Now that they’ve gathered data on Opportunity’s traction on this angle, the rover team will analyze it to understand if entering or exiting the crater is going to pose a hazard.

Original Source: Rover status report

First Image from Phoenix Mars Lander

2007-0907mpl.thumbnail.jpg

I’m not sure what you were expecting, but here’s the first image captured by NASA’s Phoenix Mars Lander from space. What, you were expecting blackness and maybe a star or two? Nope, this is a photo taken by the lander’s robotic arm showing its scoop nestled inside the spacecraft. But don’t worry, in just a few months, you’ll be seeing the same picture, but filled with Martian soil.

The image was captured by the lander’s Robotic Arm Camera, which was pointed into the robotic arm’s scoop. Both instruments are encased in a protective biobarrier that insures Earth-based microbes don’t contaminate its experiments. Surprisingly, this is going to be the only picture the camera is going to take before the spacecraft lands on Mars. I guess, this same shot might get a little boring.

Once it reaches Mars, the spacecraft will use this robotic arm to dig trenches in the Martian polar soil. It’ll scoop up soil and water-ice samples, and then deliver them to several instruments on the lander’s deck. These will test the samples for water, chemicals, and even the byproducts of past or present life.

The camera that took this picture is attached to the robotic arm, just above the scoop. It’ll provide close up images of the Martian surface, and help scientists decide where they’re going to dig for samples.

Original Source: UA News Release

How’s Phoenix Doing?

2007-0905phoenix.thumbnail.jpg

Time really flies. It’s already been a month since NASA’s Phoenix Mars Lander blasted off for the Red Planet, so I’m sure you’re wondering, how’s the spacecraft faring up so far? Pretty good actually. The Phoenix flight operations team recently checked in with the spacecraft, and made sure its most crucial instruments (well, for the landing anyway) are working properly.

Phoenix Mars Lander launched on August 4, 2007 from Florida’s Cape Canaveral, and won’t arrive at Mars until May 25, 2008. During its entire journey, the spacecraft is communicating back to Earth using a high frequency X-band transmitter. This transmitter is only temporary, however. Once the spacecraft arrives at Mars, it’ll jettison a portion of the spacecraft – where this transmitter is located – and from then on out, it’ll be relying on its UHF radio.

When landing day arrives, this radio absolutely has to be working.

Another instrument that needs to be working is its landing radar. This instrument will be constantly measuring the distance to ground as the spacecraft passes through the Martian atmosphere. A whole string of activities rely on the spacecraft being able to accurately gauge its distance to the ground for the last 3 minutes of its descent.

So, NASA tested them out. The flight operations team tested the UHF radio and its landing radar on August 24th, and made sure they were working properly. The radio won’t be turned on again until landing day on May 25th, 2008. The team also tested out one of the spacecraft’s science experiments, the Thermal and Evolved-Gas Analyzer, which will look for water and carbon-containing molecules in the icy soil at its landing site at the Martian north pole. More tests of other instruments are planned for October.

Mars Phoenix Lander has already traveled more than 81 million km (50 million miles). That sounds like a lot, and it is, but the spacecraft still has another 600 million km to go.

“Everything is going as planned. No surprises, but this is one of those times when boring is good,” said Barry Goldstein, Phoenix project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

That’s good, it’s boring now, but it’s going to be insane on May 25th… I can’t wait.

Original Source: NASA/JPL News Release

Podcast: Mars

mer-high-1_br.thumbnail.jpg

Today we consider Mars, the next planet in our journey through the Solar System. Apart from the Earth, it’s the most explored planet in our Solar System. Even now there are rovers crawling the surface, orbiters overhead, and a lander on its way. It’s a cold, dry desert, so why does this planet hold such fascination?

Click here to download the episode

Mars – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Rovers Hit the Road Again

2007-0831rovers.thumbnail.jpg

After being threatened by darkening dust storms, NASA’s Mars Exploration Rovers are ready to hit the road again. Both Spirit and Opportunity still face dusty skies, but they’re getting enough light through to their solar panels that they’re able to spare some battery power to start driving.

On August 21st, Opportunity moved ahead 13.38 metres (44 feet) towards the edge of Victoria Crater. This is the large impact crater that the rover has been studying for the last few months. Its next big job will be to work its way down a ramp into the crater, observing the layered rock as it descends. The crater serves as a time machine, allowing Opportunity to measure rock that was deposited during periods when the planet was much younger. The hope, of course, is for Opportunity to discover periods when the region was acted upon by water for long spans of time.

Opportunity’s total power supply reached 300 watt-hours on August 23, which is twice what it received 5 weeks ago. It’s enough to move and communicate, but mission controllers want it to get back into the 600+ watt-hour range that it had several months ago. If it wanted to, Opportunity could run a 100 watt light bulb for 3 hours.

The rover has been driven towards the rim of Victoria crater to put it at a favourable angle, pointing its solar panels towards the Sun. That way if further dust accumulates on its solar panels, it’ll still be able to generate enough power. But gusts of wind have actually been clearing off the panels, giving it more and more power each day.

To see what the rovers faced during the dust storms, check out this link to a Cornell University article. It has animations of the Sun each day, so you can see there was a long span in July when Opportunity couldn’t see the Sun at all.

Original Source: NASA/JPL News Release

Not Pits, Tubes

psp_004847_1745_redbrowse-1.thumbnail.jpg

Remember those amazing images of open pits on Mars? NASA’s Mars Reconnaissance Orbiter has come back around and taken another image of one of the features, and this time it spotted a wall on one side. This wall indicates that these “pits” are probably tunnels, similar to surface features on Earth called “pit craters”.

The new images were captured with the orbiter’s High Resolution Imaging Experiment (HiRISE), the most powerful camera ever to orbit another planet. It first noticed the features on May 5th, 2007. In its original image, MRO captured a photo from almost directly overhead, and saw only darkness. This time around, on August 8th, it captured the image from the west, when the Sun was also shining at an angle, revealing a wall on the eastern side of the pit.

The rim of the pit is 150 by 157 metres across. And the new image shows that the depth is at least 78 metres deep.

Here on Earth, you can find pit craters in Hawaii, around the Kilauea Volcano. They’re circular-shaped craters that are believed to form when a magma lake empties out underneath. The crusty top then collapses down forming a bowl shaped crater. For example, here’s a link to an image of a pit crater in Hawaii.

This isn’t the first time that pit craters have been seen on Mars. For example, here’s another image captured by HiRISE of pits along the floor of Cyane Fossae, a set of fissures between the giant volcanoes Olympus Mons and Alba Patera. These fissures formed when the surface of Mars was being stretched by volcanic activity, causing underground voids to collapse. But these are much shallower than the newly discovered “pit”.

New Scientist is covering this story from the angle that these pits could serve a refuge for astronauts, protecting them from the dangerous ultraviolet radiation streaming from the Sun. Unlike the Earth, Mars has no protective ozone layer that blocks ultraviolet radiation. These pits could provide a wall of nice protective dirt, assuming they remain in the shadows.

I’m sure we’ll hear more on this story in the weeks and months to come. It’s very exciting.

Original Source: University of Arizona News Release

Phoenix Makes a Course Correction

phoenix.thumbnail.jpg

NASA’s Phoenix Mars Lander is right on schedule for its 2008 visit with the Red Planet. But between now and then, it’s got some work to do. Late last week it completed its first task, performing a course correction to bring into a perfect trajectory to reach Mars; it has 5 more to do over the course of the mission.

Phoenix is currently hurtling towards Mars at a velocity of about 33,180 metres per second (74,200 mph) in relation to the Sun. This first trajectory maneuver tweaked its velocity by about 18.5 metres per second (41 mph). The spacecraft fired its four thrusters for a total of 3 minutes and 17 seconds to make the adjustment.

It sounds like everything went according to plan. According to Joe Guinn, Phoenix mission system manager at NASA’s Jet Propulsion Laboratory, “all the subsystems are functioning as expected with few deviations from predicted performance.” Yeah… what he said.

The next intentional course correction is scheduled for mid-October.

Believe it or not, Phoenix was launched on an incorrect trajectory intentionally. Without these course corrections, the spacecraft would miss Mars by about 950,000 km (590,000 miles). This was done so that the spacecraft’s third-stage rocket booster won’t hit Mars. With the intentional incorrect trajectory, the third stage will sail by the Red Planet, while Phoenix can still enter its atmosphere. The lander is carefully cleaned to ensure no bacteria reach the Martian surface, while the booster remains contaminated with Earth’s bacteria. We wouldn’t want to infect Mars with our life.

Original Source: NASA News Release

Martian Skies are Starting to Clear

spitir.thumbnail.jpg

The dire condition of the Mars Exploration Rovers has improved a bit in the last few days. That series of dust storms circling the planet has eased off a little, and the skies are started to clear up. This is giving both Spirit and Opportunity a much needed boost to their solar powered electrical systems.

On August 6th, 2007 Spirit’s solar arrays collected a total of 295 watt hours; Opportunity gathered 243 watt hours. This is a significant improvement over the last few weeks, when the dust storms dropped Spirit down as low as 261 watt hours, and Opportunity down to 128. At those levels, engineers were worried that the rovers might not be able to even keep their sensitive electronics heated overnight.

With the skies clearing up, Spirit even has enough energy to start doing some science again. Operators will command the rover to move its robot arm for the first time in three weeks. Its job will be to position its microscopic imager to take a series of photographs of two soil targets and a rock target. Opportunity will stay put, but make observations of the Martian atmosphere.

The increased sunlight has allowed both rovers to fully recharge their batteries, and the night time temperatures have warmed up a little, decreasing the risk of freezing their electronics.

NASA managers are still pretty wary, though, and have a cautious take on the situation:

“Conditions are still dangerous for both rovers and could get worse before things get better,” said John Callas, rover project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

“We will continue our cautious approach to the weather and configure the rovers to maintain a high state of charge on the batteries. Communication sessions with both rovers will remain limited until the skies clear further.”

Sounds like a good idea.

Original Source:NASA News Release