Author: Nancy Atkinson

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Scientists from the Phoenix Mars Lander mission say the lander uncovered clues that the Martian arctic soil has been warmer and wetter in the past, and right now Mars may just be in a dry cycle. The biggest clue is the “clumpiness” of the soil in the Mars arctic region that Phoenix encountered, making it difficult for the lander to dump samples into the “ovens” that analyzed the chemistry of the soil. While currently the soil is cold and dry, when long-term climate cycles make the site warmer, the soil may get moist enough to modify the chemistry, producing effects that persist through the colder times. “We have snowfall from the clouds and frost at the surface, with ice just a few inches below, and dry soil in between,” said Phoenix Principal Investigator Peter Smith of the University of Arizona , Tucson . “During a warmer climate several million years ago, the ice would have been deeper, but frost on the surface could have melted and wet the soil.”

With no large moon like Earth’s to stabilize it, Mars goes through known periodic cycles when its tilt becomes much greater than Earth’s. During those high-tilt periods, the sun rises higher in the sky above the Martian poles than it does now, and the arctic plain where Phoenix worked experiences warmer summers.

“The ice under the soil around Phoenix is not a sealed-off deposit left from some ancient ocean,” said Ray Arvidson of Washington University in St. Louis , lead scientist for the lander’s robotic arm. “It is in equilibrium with the environment, and the environment changes with the obliquity cycles on scales from hundreds of thousands of years to a few million years. There have probably been dozens of times in the past 10 million years when thin films of water were active in the soil, and probably there will be dozens more times in the next 10 million years.”

Cloddy texture of soil scooped up by Phoenix is one clue to effects of water. The mission’s microscopic examination of the soil shows individual particles characteristic of windblown dust and sand, but clods of the soil hold together more cohesively than expected for unaltered dust and sand. Arvidson said, “It’s not strongly cemented. It would break up in your hand, but the cloddiness tells us that something is taking the windblown material and mildly cementing it.”

That cementing effect could result from water molecules adhering to the surfaces of soil particles. Or it could be from water mobilizing and redepositing salts that Phoenix identified in the soil, such as magnesium perchlorate and calcium carbonate.

The Thermal and Electrical Conductivity Probe on Phoenix detected electrical-property changes consistent with accumulation of water molecules on surfaces of soil grains during daily cycles of water vapor moving through the soil, reported Aaron Zent of NASA Ames Research Center, Moffett Field, Calif., lead scientist for that probe.

“There’s exchange between the atmosphere and the subsurface ice,” Zent said. “A film of water molecules accumulates on the surfaces of mineral particles. It’s not enough right now to transform the chemistry, but the measurements are providing verification that these molecular films are occurring when you would expect them to, and this gives us more confidence in predicting the way they would behave in other parts of the obliquity cycles.”

Phoenix worked on Mars this year from May 25 until November 2.The Phoenix science team will be analyzing data and running comparison experiments for months to come. Today, they reported on some of their progress at a meeting of the American Geophysical Union in San Francisco.

Source: NASA

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Grab your 3-D glasses and prepare to be amazed (and addicted!) The team from the remarkable HiRISE Camera on board the Mars Reconnaissance Orbiter has released a collection of 3-D images — 362 of ’em — of Mars surface. The incredible power of this camera can resolve features as small as one meter, or 40 inches, across, and in looking at these 3-D images, it’s almost like being there. Above is one of my favorites from this collection, Arabia Terra. “It’s really remarkable to see Martian rocks and features on the scale of a person in 3-D,” said Alfred McEwen of UA’s Lunar and Planetary Laboratory, HiRISE principal investigator. “The level of detail is just much, much greater than anything previously seen from orbit.”

How was the team able to create so many 3-D images? And how can you get or make a pair of 3-D glasses?

Usually, creating 3-D anaglyphs is a tedious and time-consuming process. But the HiRISE team was able to automate some of the software used in processing the images so two images of a stereo pair could be fed into the software “pipeline” and correlated automatically. So look for even more 3-D images in the future. But 362 should keep most of us busy, for awhile anyway!

Here, spectacular layers are exposed on the floor of a large canyon in the Valles Marineris system called Candor Chasma which is about 2-and-a-half miles, or 4 kilometers deep. The canyon may once have been filled to its rim by sedimentary layers of sand and dust-sized particles, but these have since eroded, leaving patterns of elongated hills and layered terrain that has been turned and folded in many angles and directions.

If you don’t have a pair of 3-D glasses, here’s a link to a list of several sources of finding some, or you can even make your own. Sometimes, 3-D glasses can be found for free on cereal boxes, or in children’s books or other sources.

Find out how 3-D images are made, and learn how to make your own 3-D images here.

Here is a 3-D version of Becquerel Crater, and the layered terrain of which we wrote about last week, which was formed by cyclical climate change.

See the entire collection of HiRISE 3-D’s here.

Source: U of Arizona

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We see evidence on Mars’ surface of a violent past: massive volcanic eruptions, catastrophic floods, and a surface scarred with craters. But new images of rock formations on Mars resembling stairs suggest Mars at one time had a regular pattern of predictable and even moderate climate cycles persisting for millions of years. Three-dimensional images from the HiRISE camera on the Mars Reconnaissance Orbiter show patterns in thick stacks of sedimentary rock layers, formed by a cyclical climate that is likely tied to the wobble of Mars on its axis.

Combining several images of the rock formations from different perspectives, scientists were able to produce three dimensional images, as well as a dramatic flyby movie of the layered sediments. Based on a pattern of layers within layers found at an area called Becquerel crater, the scientists propose that each layer was formed over a period of about 100,000 years and that these layers were produced by cyclical climate changes. The outcrops have been eroded into mounds on the floors of the craters, with many of the layered deposits showing a stair-stepped shape. Each layer has exactly the same thickness.

Every 10 of the “staircase” layers are bundled into a larger unit, which the team, led by Kevin Lewis of the California Institute of Technology, calculates was laid down over a million-year period, and Becquerel contains 10 of these bundles. One million years is the same duration as the periodic variations in Mars’ tilt, suggesting that climate variations induced by the tilt produced the layering. Each bundle, then, represents climate processes as the planet tilted. This tilt periodically cooled the equatorial region and warmed the poles as they received more sunlight.

“Due to the scale of the layers, small variations in Mars’s orbit are the best candidate for the implied climate changes,” said Kevin Lewis of the California Institute of Technology, who led the study. “These are the very same changes that have been shown to set the pacing of ice ages on the Earth and can also lead to cyclic layering of sediments.”

The tilt of Earth on its axis varies between 22.1 and 24.5 degrees over a 41,000-year period. The tilt itself is responsible for seasonal variation in climate, because the portion of the Earth that is tipped toward the sun–and that receives more sunlight hours during a day–gradually changes throughout the year. During phases of lower obliquity, polar regions are less subject to seasonal variations, leading to periods of glaciation.

Mars’s tilt varies by tens of degrees over a 100,000-year cycle, producing even more dramatic variation. When the obliquity is low, the poles are the coldest places on the planet, while the sun is located near the equator all the time. This could cause volatiles in the atmosphere, like water and carbon dioxide, to migrate poleward, where they’d be locked up as ice.

“It’s easy to be fooled without knowing the topography and measuring the layers in three dimensions,” said Alfred McEwen of the University of Arizona, Tucson, principal investigator for the camera and a co-author of the paper. “With the stereo information, it is clear there’s a repeating pattern to these layers.”

Sources: JPL, Caltech