Category: Mars

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A new study of gullies seen on Mars provides evidence that water flowed recently on the Red Planet, at least in geologic terms. Planetary geologists at Brown University have found a gully fan system on Mars that formed only about 1.25 million years ago. The structure of this fan offers compelling evidence that it was formed by melt water that originated in nearby snow and ice deposits. This time frame may be the most recent period when water flowed on the planet. This most recent finding comes on the heels of discoveries of water-bearing minerals such as opals and carbonates, and together all these discoveries provide clues that Mars was, at least occasionally, wetter and warmer for far longer than previously thought.

While gullies are known to be young surface features, it’s difficult to date them. But the Brown scientists were able to date the gully system because of craters in the area, and also hypothesize what water was doing there.

The gully system shows four intervals where water-borne sediments were carried down the steep slopes of nearby alcoves and deposited in alluvial fans, said Samuel Schon, a Brown graduate student and the paper’s lead author.

“You never end up with a pond that you can put goldfish in,” Schon said, “but you have transient melt water. You had ice that typically sublimates. But in these instances it melted, transported, and deposited sediment in the fan. It didn’t last long, but it happened.”

The gully system is located on the inside of a crater in Promethei Terra, an area of cratered highlands in the southern mid-latitudes. The eastern and western channels of the gully each run less than a kilometer from their alcove sources to the fan deposit.

Viewed from afar, the fan appears as one entity several hundred meters wide. But by zooming in with the HiRISE camera aboard the Mars Reconnaissance Orbiter, Schon was able to distinguish four individual lobes in the fan, and determine that each lobe was deposited separately. Moreover, Schon was able to identify the oldest lobe, because it was pockmarked with small craters, while the other lobes were unblemished, meaning they had to be younger.

Next came the task of trying to date the secondary craters in the fan. Schon linked the craters on the oldest lobe to a rayed crater more than 80 kilometers to the southwest. Using well-established techniques, Schon dated the rayed crater at about 1.25 million years, and so established a maximum age for the younger, superimposed lobes of the fan.

The team determined that ice and snow deposits formed in the alcoves at a time when Mars had a high obliquity (its most recent ice age) and ice was accumulating in the mid-latitude regions. Sometime around a half-million years ago, the planet’s obliquity changed, and the ice in the mid-latitudes began to melt or, in most instances, changed directly to vapor. Mars has been in a low-obliquity cycle ever since, which explains why no exposed ice has been found beyond the poles.

The team tested other theories of what the water may have been doing in the gully system. The scientists ruled out groundwater bubbling to the surface, Schon said, because it seemed unlikely to have occurred multiple times in the planet’s recent history. They also don’t think the gullies were formed by dry mass wasting, a process by which a slope fails as in a rockslide. The best explanation, Schon said, was the melting of snow and ice deposits that created “modest” flows and formed the fan.

The team’s findings appear in the March issue of Geology.

Source: Brown University

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A future Mars mission could include instruments attached to balloons, providing the capability to study places where rovers can’t go, while offering a closer look than orbiting satellites. NASA has awarded a Small Business Innovative Research (SBIR) Phase I contract to Aurora Flight Sciences and its partner Vertigo Inc, to develop an autonomous balloon launcher to operate from the surface of Mars. Aurora is looking to develop a compact lightweight system that could be included on future Mars landers, augmenting the mission with a small aerial vehicle. Such a system would have potential for atmospheric sampling and video data capture unavailable on current Mars missions.

Balloon-based Mars exploration has the capability to cover a larger portion of the Martian surface than is accessible via a rover and to provide better resolution than is available from satellites. Balloons could be used to measure atmospheric data at different altitudes and locations on Mars.

“A major challenge to ground deployment is the possibility of the envelope being damaged by winds, surrounding rocks, or parts of the associated lander,” said the project’s manager, George Kiwada. “Our Shielded Mars Balloon Launcher (SMBL) concept addresses this challenge by using inflatable structures to provide a safe environment for balloon inflation and deployment.”

Balloons have been flying for decades in Earth’s stratosphere, which has an atmosphere as thin as that on the surface of Mars. Conventional stratospheric balloons have lifetimes limited to a few days because of the daily heating and cooling of the balloon. Helium superpressure balloons, currently under development for the Ultra Long Duration Balloon (ULDB), will fly more than 100 days and perhaps as long as a year. Smaller superpressure balloons carrying payloads of only a few kilograms have already flown for as long as a year.

Aurora’s has done previous work with NASA on the development of a Mars airplane. In that project, Aurora became familiar with the challenges of aerial vehicle operations in the Martian atmosphere.

Source: Aurora Flight Sciences

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Liquid water may have been discovered by the late Phoenix Mars Lander. This astonishing (and controversial) claim comes from some very intriguing images of the lander’s leg shortly after Phoenix landed on the Red Planet last year. The series of black and white images appear to show droplets of water hanging off the robot’s bodywork in the shade; it seems possible that the water droplets were splashed from the surface during Phoenix’s rocket-assisted landing. Far from being static blobs, they appear to grow, much like water droplets here on Earth as water vapour is absorbed from the atmosphere.

But wait a minute, isn’t the Martian atmosphere too thin and too cold to accommodate liquid water? That’s where the perchlorate comes in…

If liquid water has been found to exist on the surface of Mars, there will be huge implications for our understanding of the planet. Most tantalizingly, liquid water, on or near the planet’s surface, could aid the survival of microbial life, reinvigorating the search for extraterrestrial life on out interplanetary neighbour. But on a planet where the atmospheric pressure is 100 times less than on Earth, and temperatures reached a maximum of -20° Celcius during the Phoenix mission, why isn’t this “liquid water” candidate frozen?

The perchlorate discovery in the Martian soil was announced by the Phoenix team in August 2008, after an explosion of intense Internet conjecture caused by the “potential for life” announcement by an Aviation Week article days earlier. It turned out that the Phoenix instrumentation had found quantities of a toxic chemical called perchlorate known to be a hindrance to life as we know it. Although follow-up reports were slightly more positive about the presence of the chemical (a possible energy source for microbial life), the mood was fairly sombre. On a planet as unforgiving as Mars, any bad news is a severe knock for the hope of finding life.

However, regardless of perchlorate’s toxic effects on life, it may be helping out another one of life’s resources to stay in liquid form. If perchlorate is dissolved in significant quantities, water could remain as a liquid down to temperatures as low as -70°C. So could it be that the dissolved perchlorate salt is acting as a very impressive anti-freeze?

Nilton Renno from the University of Michigan and Phoenix team member, thinks it could be. “According to my calculations, you can have liquid saline solutions just below the surface almost anywhere on Mars,” he said.

Renno’s team carried out a series of laboratory experiments and found that the lander’s thrusters would have melted the top millimetre of ice in the regolith. The resulting water droplets may have been splashed onto the landers leg. If the concentration of perchlorate was high enough, the water could have remained in a liquid state during the Mars daytime. As time progressed, atmospheric water vapour may have been absorbed, hence the growing and shifting blobs of liquid on the leg. There is also the possibility that the droplets were splashed from pools of perchlorate-rich water already in a liquid state on the surface.

However, not everyone is convinced. Fellow Phoenix team member Michael Hecht from NASA’s Jet Propulsion Laboratory in Pasadena, California, thinks that the photographs actually show water ice, not liquid water. The “frost” changed shape as vapour from the air coalesced and froze to the leg. Renno points out that this is unlikely as any ice on the leg would be more likely to sublime, rather than grow, but Hecht believes this could happen if the leg was colder than its surroundings.

Renno’s team will be continuing tests on samples of perchlorate-rich water under Mars-like conditions for the next few months to understand the dynamics of water under these extreme conditions. What makes this even more interesting is that some microbial life on Earth has the ability to survive in very salty fluids, perhaps microbial alien life on Mars evolved in a similar environment where there were pools of liquid water maintained at extremely low temperatures by high concentrations of perchlorate salt…

Source: New Scientist