May 3, 2008

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM): Exclusive Interview with Mission Scientist Dr Adrian Brown

Water will be one of the most critical factors influencing any long-term manned mission to Mars. Will there be ample surface ice that can be mined and melted? Are there sub-surface aquifers colonists can "tap" into? Is there enough water vapour in the atmosphere that can be condensed and stored?

We've heard the possibilities of sending an advanced team of robots to extract and store atmospheric water, there are also plenty of ideas of how we could mine solid ice and subsurface supplies. But wait a minute, where would we search for this water? In what form can we expect it to be in? Has there been water existing on the surface in the past? All these questions (and a lot more besides) are beginning to be answered by the three spacecraft currently in orbit around the Red Planet. NASA's Mars Reconnaissance Orbiter (MRO), Mars Odyssey and ESA's Mars Express are all operational, looking down on Mars. But the MRO has a special device on board: The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).

Dr Adrian Brown, SETI Institute principle investigator at the NASA's Ames Research Center in Moffett Field, California, is one of the scientists analysing the data being collected by CRISM and has kindly taken some time to talk with the Mars Foundation about his work... [more]

Dr Brown's interest in Mars was sparked after reading "The Case for Mars" by Robert Zubrin, founder of the Mars Society. At the time Adrian was in the Royal Australian Navy sailing in Hawai'ian waters keeping an eye open for the "bad guys", but from this point on he became fascinated with the Red Planet and began looking for an alternative way to "win a small victory for mankind". It would appear he too fell for the allure of exploring Mars.

An Australian citizen, Brown moved to California after completing his PhD in Earth and Planetary Science at Macquarie University, in Sydney. His thesis was titled "Hyperspectral Mapping of Ancient Hydrothermal Systems". The CRISM project gave him the opportunity to expand on his PhD and work on analysing the icy Martian polar regions. He is currently studying the seasonal processes at the south pole of Mars. It is hoped that a quantitative analysis of the amount of water and CO₂ ice held on the surface and in the atmosphere may be derived.

Plentiful Water Ice

It appears the north polar region of Mars already has plenty of water ice to spare. According to Brown's estimate, the north pole can be thought of as a disk of near-pure water ice (including dirt from dust and other impurities) with a diameter of about 1000 km (620 miles) with a depth of 3 km (1.9 miles); that's a staggering volume of 2.35 million cubic kilometres – enough water to cover the continental US to a depth of over 200 meters.

The southern ice cap is a different story. It too holds a small disk of water ice (300 kilometers in diameter), only below a thin layer of CO₂ ice. Although small, this ice cap reaches 2 km (1.24 miles) in height, and ignoring the CO₂ and other impurities, there's about 140 thousand cubic km of pure water, enough to cover the continental US to a depth of 14 meters.

So, there's quite a lot of water then? To put this in perspective, Brown points out that this is about as much water held in the Greenland ice sheet, and 500 times less than the total volume of water in our oceans. At least we know there is a large potential source of water ice easily accessible on the surface for Mars colonies to mine.

Heating Permafrost and Aquifers

Dr Brown then indicates that there may be substantial quantities of water held below the surface too and highlights the Phoenix mission as a possible lander that could uncover more secrets about what lies beneath:

"In fact, we also know there is a large amount of permafrost in both poles, poleward of 60 degrees latitude, and we'll find out more about that reservoir when Phoenix lands there on 25 May. What we know now from the Gamma Ray and Neutron Detector instruments on Mars Odyssey is that a large amount of water ice is trapped in the subsurface of the polar regions. For settlers willing to settle the flat wastes of Utopia Planitia, north of 60 degrees latitude, they will simply have to drill, heat, and repeat to get all the water they like. Phoenix will be the first robotic probe to try this strategy." - Dr Adrian Brown

There is also the possibility of finding liquid water under the surface. Brown points out the sporadic discharges of water around the warmer equatorial regions that may have created the gullies as observed by the Mars Orbiter Camera (MOC). These gullies may provide some clues as to where colonists may drill to seek out these aquifers.

Atmospheric Ice Crystals

But what about the water vapour in the atmosphere? CRISM actually wasn't designed to detect vapour in the atmosphere, but it can detect water ice crystals, which is useful as in polar regions water vapour will condense and freeze very quickly. So the work being carried out focuses on analysing atmospheric water ice and mapping it throughout the Mars seasons to see how it varies. This study may help to explain why the north polar region is more rich in water ice than the south.

When asked whether the atmospheric ice crystals would be useful to Mars colonists, Brown draws some parallels with some methods of extraction as commonly seen in science fiction:

"Absolutely - colonists would be able to use Martian [atmospheric] water, though of course it would be a far more precious resource than here on Earth. Think 'Arrakis' from Dune - stillsuits could be a normal part of the life of future Martian colonists. Water vapour and water ice clouds are a normal part of Martian seasons and they'd require distilling (think of Uncle Owen's vapour farm on Tatooine [in "Star Wars: A New Hope"]) but they may be a way for colonists far from the Tharsis or Elysium regions to collect water." - Dr Adrian Brown

Although the hunt and characterization of water on Mars is highly important, the CRISM instrument has many other accolades. Since beginning its operations in 2006, CRISM has discovered new phyllosilicate minerals on the surface, but the mission scientists are trying to understand how they got there in the first place. "These include kaolinite (chinaware is made of this mineral), talc (the main constituent of many soaps) and hydrated silica (perhaps like chert, which Indian knives were carved out from)," Brown continued, "the small amounts of these minerals means it has been impossible to discover them before CRISM, and previously they were discounted in all our modeling of Mars." Now it seems CRISM is beginning to rewrite the Mars history books as these minerals have been previously discounted.

Wrapping up our interview, I asked Adrian if he personally wanted to experience Mars, if so, what he would like to see the most:

"Of course I would love to travel to Mars, most of all to go to the polar regions and observe them with my own eyes. If I could actually go to the surface of Mars to investigate the fascinating geology of Nili Fossae and Valles Marineris, that would be so awesome. And to visit a gully site and dig behind it to try and find its source... and to witness the cold volcanoes of mud that erupt in the polar cryptic region during springtime... to go and understand these things that have us puzzled at the moment would be so amazing... and of course more questions would be raised, more geological problems unearthed, and the cycle of understanding the Red Planet would continue." - Dr Adrian Brown

I share his enthusiasm and I'm sure many Mars settlement advocates feel the same way. For me, I'd join Adrian for that trip to Vallis Marineris, the largest valley in the Solar System, and I too would be intrigued to really see where the source of the Mars gullies lead.

An inspiring insight to an incredible instrument orbiting Mars, so thank you Dr Brown for your time in answering my questions. If you are interested in Dr Brown's work and would like to read more, visit his project website (http://abrown.seti.org/index.html). You can also read more about the CRISM instrument at NASA's CRISM web site (http://crism.jhuapl.edu/).

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