Red Planet, Icy World? New Picture of Ancient Mars Emerges

Ancient Mars may have been an icy realm and not the warm, wetter environment scientists had thought, a new study suggests. See what it means for life. Continue reading →

Ancient Mars might have looked more like an icy snowball than the warmer, wetter planet that many researchers have suggested, according to a new study. The study suggests that channels seen on the Red Planet's surface are better explained by erosion from ice and snow runoff - and not by flowing water - in the ancient past.

But if ancient Mars was, indeed, an icy wasteland, that would have made it harder for potential life to take hold 3 billion or 4 billion years ago, researchers behind the study say.

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"I'm still trying to keep an open mind about this," Robin Wordsworth, the study's lead author and an assistant professor at the Harvard School of Engineering and Applied Sciences, said in a statement. "There is lots of work to be done." [The Search for Water on Mars in Photos]

Wordsworth and his collaborators arrived at this conclusion after running 3-D atmospheric models to see how water moved between Mars' surface and its atmosphere billions of years ago.

The first scenario envisioned Mars as a temperate place, with an average global temperature of 50 degrees Fahrenheit (10 degrees Celsius). The second scenario then cast the Red Planet into ice-ball conditions, with an average global temperature of minus 54 F (minus 48 C).

The results showed that the "cold" model did a better job of eroding features on the planet's surface similar to those observed by spacecraft currently on and orbiting Mars. Further, the researchers said the "cold model" was based on a more accurate representation of the sun's history (it was 25 percent dimmer at the time) and the way Mars' axis was tilted 3 billion to 4 billion years ago.In that scenario, Mars' poles would have been pointed at the sun, which would have caused a buildup of ice along the planet's equator.

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There also would have been a thicker atmosphere that would have exaggerated the effect: The equator highlands would have been cold, and the lower lands at the poles would have been warm.So, is it possible that Mars was warm and wet? The scientists said that scenario is more unlikely, as previous work shows that carbon dioxide, dust and clouds are still not quite enough to make the planet that way.

After adding more effects to their model, however, the scientists came up with a scenario where rainfall changed greatly across the planet. Arabia and the Hellas basin, where there are few erosion features spotted today, would have been the wettest areas, the researchers said.

By contrast, the model showed some of the places with the most erosion features (such as Margaritifer Sinus) were almost dry. This is because, just as on Earth, mountains created rain shadows in certain regions on Mars. Specifically, the Red Planet's Tharsis region would have created rainfall on the western (windward) side, while Margaritifer Sinus was on the eastern and drier side.

A paper based on the work has been accepted for publication in the American Geophysical Union's Journal of Geophysical Research: Planets.

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This image paints two very different views of ancient Mars: one warm and wet (top left), and the other a frozen, icy world.

Watching a sunset on Earth can be a dazzling and beautiful natural wonder. But what about sunsets on other worlds? Situated over 50 percent further away from the sun than Earth, there's one planet that we've also had the fortune to see the sun drop below the horizon while standing on the surface -- Mars. However, we have yet to experience this Martian perspective with our


eyes; instead we depend on images beamed to Earth after being witnessed by robotic lenses and CCDs from NASA's landers and rovers.

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Our first robotic views of a Martian sunset came from NASA's Viking Program, which set two landers down on the Martian surface in 1976. Viking 1 operated until 1980, whereas Viking 2 survived until 1982. In this observation by Viking 1 across the mission's landing site of Chryse Planitia, one of the lander's many sunsets was imaged 30 Martian days (sols) after touch down. The banding in the sky "is an artifact produced by the incremental brightness levels of the camera,"

according to NASA


On July 4, 1997, NASA returned to the Martian surface with the Mars Pathfinder mission that consisted of a lander and the first successful Mars rover called "Sojourner." With improved optics, better views of the Martian atmosphere and landscape were possible. Captured on sol 21 of the mission, this view of a sunset behind two prominent hills nicknamed "Twin Peaks" is as striking as it is scientifically important. Pathfinder's lander used its optical instrumentation to measure the dusty particles the setting sunlight was passing through, boosting our understanding of the Martian atmosphere.

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Where there's a sunset, there's also a sunrise. The Pathfinder mission captured this series of photographs just as dawn was breaking over Chryse Planitia on sol 25 of the mission. While the sun was low on the horizon, Pathfinder was also able to image high-altitude clouds of ice glinting in the sunlight.

PHOTO: A Blue Sunset On Mars

NASA's Mars rover Spirit captured probably one of the most famous scenes to ever come from Mars. With a bluish inverted triangle of light emanating from a setting sun, giving way to a brownish sky, this view across Gusev Crater captivated the world.

The image was captured on the 489th sol

after landing on the Red Planet in January 2004. Spirit, along with sister rover Opportunity, had a prime mission of only 3 months. When Spirit photographed this dreamy scene it was already operating a year longer than intended. The rover would continue to explore Gusev Crater until it became stuck in a sand trap in 2009. NASA lost contact with the stranded robot and officially ended its epic adventure in 2010.

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The Phoenix Mars Lander was an arctic explorer. Landing in the northern hemisphere's late spring, the solar-powered robot enjoyed 3 months of continuous sunlight at its high latitude location. But as the mission continued, the sun slowly dipped toward the horizon, reducing the intensity of sunlight until it was finally lost. In

this series of observations

recorded on Sept. 5, 2008, the sun can be seen skirting along the silhouetted horizon, emerging from a lazy sunset into sunrise.

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NASA's Mars rover Opportunity is no stranger to Mars sunsets. Landing on Mars within weeks of its rover twin Spirit, Opportunity continues to doggedly explore Mars to this day. 11 years of continuous operations

has taken its toll

, but having recently completed

the first ever marathon on an alien world

, Opportunity is the reigning champion of Mars roving. And with all that roving has come thousands of Mars sunsets and sunrises.

This particular view was captured on Nov 5, 2010

, when the rover was traversing the plains of Meridiani Planum, heading to its current area of study, Endeavour crater.

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Mars rover Curiosity is the newest addition to NASA's ground campaign on the Red Planet. Landing on Aug. 6, 2012, the rover has already provided compelling evidence that the barren planet was once a lot wetter than it is now, also uncovering traces of organic compounds. These historic discoveries provide a tantalizing glimpse into Mars' geological history when it may have been habitable for microorganisms. Although Curiosity is a robotic geologist and chemist, it's also rather good at astronomy.

It has also admired the Gale Crater sunsets

, not only producing some stunning views with its high-resolution optics, but adding to our scientific understanding of atmospheric composition.

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This sequence of photos show Curiosity's view of the sun setting over Gale Crater. The strange bright bands across the sun is caused by the over-saturation of Curiosity's Mastcam CCD pixels, creating a bleeding effect across pixel rows.

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With every sunset, there's a robot's shadow. This view of Opportunity was captured in March 2014 when the sun was about to set.

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There's also no lack of photographs of Curiosity's shadow on Mars. In this stunning image, shortly after landing on the Red Planet, the nuclear-powered rover shoots its own shadow as the sun sets behind it. In the distance, Mount Sharp is illuminated in the evening sun.

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