Red Planet Roundup: September 2014

by Timothy Oleson
Tuesday, August 19, 2014

Images taken by the Mars Color Imager on March 27 (left) and March 28, 2012 (right), narrowed down the formation date of a fresh impact crater to just one day, the tightest window yet for such a feature. Credit: NASA/JPL-Caltech/MSSS.

As Curiosity and Opportunity rove around Mars, the Mars Reconnaissance Orbiter (MRO), Mars Express and Mars Odyssey orbit above, and scientists on Earth study the Red Planet from afar, new findings are announced almost weekly. Here are a few of the latest updates.

Looking through images taken by the High Resolution Imaging Science Experiment (HiRISE) and Context (CTX) cameras aboard NASA’s MRO as well as by the High Resolution Stereo Camera aboard the European Space Agency’s Mars Express, scientists have pointed out landforms in Mars' Gale Crater that appear to have been shaped by ancient glaciers about 3.5 billion years ago. In a study in Planetary and Space Science, lead author Alberto Fairén of Cornell University and colleagues noted lobate formations, moraines, fan-shaped deposits and other features. On Earth, such landforms are often indicative of glacial and glaciofluvial (stream discharge from glaciers) processes acting on landscapes. “For example, there is a glacier on Iceland — known as Breiðamerkurjökull — which shows evident resemblances to what we see on Gale Crater, and we suppose that is very similar to those which covered Gale’s central mound in the past,” Fairén said in a statement. The study offers “strong local support for the global ‘cold and wet' model of the ancient Martian environment,” Fairén said, “which explains both the geological traces of the presence of liquid water in the past … together with the climatic models, which have demonstrated that Mars was never a warm planet.”

In other glacially themed Mars news, evidence of lava-ice interactions on the Red Planet’s third-tallest volcano, Arsia Mons, indicates that large “englacial” pockets of liquid water may have formed there when volcanic eruptions melted portions of overlying glaciers roughly 210 million years ago, according to a study in the journal Icarus. Because the lakes would have been surrounded by thick glacial ice, they could have remained liquid for hundreds to thousands of years without evaporating or refreezing in Mars' thin atmosphere. That means they could have offered habitable environs — the most recent yet found — for microbes, if any were residing on the planet at the time. Other potentially habitable environments identified to date, such as Gale Crater, where Curiosity is exploring, are thought to be billions of years old. The landforms seen on Arsia Mons include steep-sided mounds and ridges that resemble terrestrial features formed when lava erupts beneath glaciers. They were observed by Kathleen Scanlon, a Brown University graduate student and lead author of the study, and colleagues in imagery collected by MRO.

Spotting fresh craters on the Martian surface is nothing new for space scientists. But until now no one had ever established the exact date of a crater-forming impact. Now, Bruce Cantor of San Diego-based Malin Space Science Systems, which operates the Mars Color Imager (MARCI) and CTX cameras aboard MRO, has. Cantor spied a dark spot on the planet’s surface in a recent MARCI image that he suspected could be a young crater. Searching back through past data from MARCI — which takes relatively low-resolution images, but covers the entire Martian surface on a daily basis — Cantor noticed that the dark spot first appeared in an image dated March, 28, 2012. It wasn’t present in imagery from the day before, however. In April, sharper images taken by the HiRISE and CTX cameras confirmed that the feature was indeed an impact crater. “Studies of fresh impact craters on Mars yield valuable information about impact rates and about subsurface material exposed by the excavations,” said Leslie Tamppari, a deputy project scientist for MRO, in a press release.

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