HiRISE Highlights: Crater Within a Crater, Awesome View of Victoria and More

I was just thinking it had been awhile since we featured images from the HiRISE camera onboard the Mars Reconnaissance Orbiter spacecraft, so I moseyed over to the HiRISE website only to be blown away by their newest releases. This incredible crater in Meridiani Planum shows a possible double whammy of impacts. It looks as though material filled in the original crater only to be blown out a second time. Another option is that the material in the crater could have collapsed, giving the appearance of a second impact. You can bet the HiRISE team will be looking more closely at this one. Before we move on to more great images, an update on MRO, which unexpectedly went into “safe” mode last week: MRO has now been restored to full operations, after switching to its backup computer. Engineers successfully transitioned the orbiter out of limited-activity “safe” mode on Saturday, Aug. 8, and resumed use of the spacecraft’s science instruments on Monday, Aug. 10. This has happened a few times, and engineers are trying to figure out the root cause of this.

Now, on to the images!
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Landforms Indicate “Recent” Warm Weather on Mars

Remember the polygon-shaped landforms at Mars north polar region that the Phoenix lander studied? The polygons are produced by seasonal expansion and contraction of ground ice, and these shapes have been found in other regions on Mars as well. New studies of images from the HiRISE camera on the Mars Reconnaissance Orbiter indicates that the Martian surface near the equator experienced freeze-thaw cycles as recently as 2 million years ago. This means Mars had significantly warmer weather in its recent past, and has not been locked in permafrost conditions for billions of years as had been previously thought.

The HiRISE images show polygon-patterned surfaces, branched channels, blocky debris and mound/cone structures.

Dr. Matthew Balme, from The Open University, made the new discovery by studying detailed images of equatorial landforms that formed by melting of ice-rich soils, such as the polygons, branched channels, blocky debris and mound/cone structures. These are all found in an outflow channel, thought to have been active as recently as 2 million to 8 million years ago. Since the landforms exist within, and cut across, the pre-existing features of the channel, this suggests that they, too, were created within this timeframe.

Full resolution view of domed polygons from HiRISE.  Credit: NASA/JPL/U of A
Full resolution view of domed polygons from HiRISE. Credit: NASA/JPL/U of A

All of these features are similar to landforms on Earth typical of areas where permafrost terrain is melting.

“The features of this terrain were previously interpreted to be the result of volcanic processes,” said Balme. “The amazingly detailed images from HiRISE show that the features are instead caused by the expansion and contraction of ice, and by thawing of ice-rich ground. This all suggests a very different climate to what we see today.”

This also means as the shorter the time period since the last warm weather on the planet, the better the chance that any organisms that may have lived in warmer times are still alive under the planet’s surface.

“These observations demonstrate not only that there was ice near the Martian equator in the last few million years, but also that the ice melted to form liquid water and then refroze,” said Balme. “And this probably happened for many cycles. Given that liquid water seems to be essential for life, these kinds of environments could be a great place to look for evidence of past life on Mars.”

Source: STFC

Looking for (Former) Lakeshore Property? HiRISE Finds It on Mars

If you’re in the market for some remote lakeshore property where you can get away from it all, this might be just what you’re looking for. Located in a secluded, pristine setting, this must-see property might be one of a kind. It’s very remote; – did I mention this lakeshore is on Mars? And, oh — it happens to be a former lakeshore.

While lakeshore property on Mars might sound like the biggest real estate swindle ever, the news of the first definitive lakeshore on Mars is momentous. Using images from the HiRISE Camera on the Mars Reconnaissance Orbiter, a University of Colorado at Boulder research team has discovered indications of a deep, ancient lake, estimated to be more than 3 billion years old.

The lake appears to have covered as much as 80 square miles and was up to 460 meters (1,500 feet) deep — roughly the equivalent of Lake Champlain bordering the United States and Canada, said CU-Boulder Research Associate Gaetano Di Achille, who led the study. The shoreline evidence, found along a broad delta in a region called Shalbatana Vallis, includes a series of alternating ridges and troughs thought to be surviving remnants of beach deposits.

“This is the first unambiguous evidence of shorelines on the surface of Mars,” said Di Achille. “The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago.”

HiRISE image from Shalbatana Vallis. Credit: NASA/JPL/ U of AZ
HiRISE image from Shalbatana Vallis. Credit: NASA/JPL/ U of AZ

An analysis of the HiRISE images indicate that water carved a 50 km (30 mile) -long canyon that opened up into a valley, depositing sediment that formed a large delta. This delta and others surrounding the basin imply the existence of a large, long-lived lake, said team member Brian Hynek, also from CU-Boulder.
“Finding shorelines is a Holy Grail of sorts to us,” said Hynek.

In addition, the evidence shows the lake existed during a time when Mars is generally believed to have been cold and dry, which is at odds with current theories proposed by many planetary scientists, he said. “Not only does this research prove there was a long-lived lake system on Mars, but we can see that the lake formed after the warm, wet period is thought to have dissipated.”

Planetary scientists think the oldest surfaces on Mars formed during the wet and warm Noachan epoch from about 4.1 billion to 3.7 billion years ago that featured a bombardment of large meteors and extensive flooding. The newly discovered lake is believed to have formed during the Hesperian epoch and postdates the end of the warm and wet period on Mars by 300 million years, according to the study.

The deltas adjacent to the lake are of high interest to planetary scientists because deltas on Earth rapidly bury organic carbon and other biomarkers of life, according to Hynek. Most astrobiologists believe any present indications of life on Mars will be discovered in the form of subterranean microorganisms.

Close-up of region in Shalbatana Vallis. Credit: NASA/JPL/U of A
Close-up of region in Shalbatana Vallis. Credit: NASA/JPL/U of A

But in the past, lakes on Mars would have provided cozy surface habitats rich in nutrients for such microbes, Hynek said.

The retreat of the lake apparently was rapid enough to prevent the formation of additional, lower shorelines, said Di Achille. The lake probably either evaporated or froze over with the ice slowly turning to water vapor and disappearing during a period of abrupt climate change, according to the study.

Di Achille said the newly discovered pristine lake bed and delta deposits would be would be a prime target for a future landing mission to Mars in search of evidence of past life.

“On Earth, deltas and lakes are excellent collectors and preservers of signs of past life,” said Di Achille. “If life ever arose on Mars, deltas may be the key to unlocking Mars’ biological past.”

The team’s paper has been published online in Geophysical Research Letters, a publication of the American Geophysical Union.