The Mars Science Laboratory (MSL) team celebrate the safe arrival of Curiosity on Mars. (image: NASA/ Bill Ingalls)
Last Friday I went to a really fascinating talk by Dr Carlton Allen, the Astromaterials Curator at the NASA Johnson Space Centre, Houston, Texas. Dr Allen is in charge of all the extraterrestrial samples collected by NASA, including those returned from the Moon during the Apollo program, all the meteorites collected in Antarctica by ANSMET, cosmic dust particles collected in the stratosphere by modified U2 aircraft and the samples returned by the Genesis and Stardust spacecrafts. Of course he doesn’t do all the work himself, he leads a team of about thirty dedicated scientists and technicians. So, if you are involved in laboratory-based studies of samples from space, Dr. Allen is a pretty good guy to know.
Computer generated oblique view of Gale Crater from the north showing the Curiosity landing ellipse. Aeolis Mons (Mount Sharp) dominates the central region of the crater. (image: NASA)
But while the curation of extraterrestrial samples is an important topic, that wasn’t what Dr. Allen had come to talk about. In fact the subject of his presentation was the geology of Gale Crater, the 154 km wide structure on Mars which is currently being studied by the Curiosity rover. With an estimated total cost of about 2.5 billion dollars, you can be sure that NASA put a lot of thought into the choice of landing site for the Mars Science Laboratory (MSL) mission. Curiosity touched down on August 6th (EDT) 2012 without a hitch using the unique “sky crane” landing system. Once it was clear that the so called “seven minutes of terror” had come to a happy conclusion, the anxious scientists and engineers at mission control were seen to erupt into a spontaneous show of unconstrained celebration. Well who can blame them?
Curiosity touching down on Mars (artist’s impression). Instead of the air bag system used on previous missions, Curiosity was deposited on the Martian surface using a “sky crane“. (image:NASA)
So what is special about Gale crater? Dr Allen explained. It is located just south of the Martian equator, close to the boundary between the southern highlands and northern plains. At the centre of the structure is a spectacular mountain “Mount Sharp” (also known as Aeolis Mons) that rises 5.5 kilometres (18,000 feet) above the crater floor. Orbital observations indicated that Mount Sharp was composed of a number of distinct packages of layered sedimentary rocks. The mountain also displays a prominent erosional unconformity. The rocks that form Mount Sharp appear to be the eroded remnants of sediments that once completely filled the crater. Mineralogical evidence suggests that the sediments on the lower slopes of the mountain were laid down in a water-rich environment, whereas further up the slope they were deposited under much dryer conditions. A critical part of Curiosity’s mission is to investigate this transition from wet to dry sedimentation.
The location of Gale Crater shown in relation to the landing sites of previous Mars’ missions. Gale Crater sits close to the boundary between the southern uplands and northern plains of Mars. (image: NASA)
Dr. Allen started his talk by emphasising the science goals of the MSL mission. It is a mission designed to investigate a site that shows clear evidence of past aqueous processes and so the research is directed at looking at whether conditions in the past were ever suitable for life. He made it clear that Curiosity is not in the business of looking for evidence of either past or present life on Mars. The MSL website is quite clear on this point: ”MSL is not a life detection mission and is not designed to detect extant vital processes that would betray present-day microbial metabolism. Nor does it have the ability to image microorganisms or their fossil equivalents”. All of which sounds a bit disappointing.
Layered sedimentary rocks at the base of Mount Sharp. (image: NASA)
I asked Dr Allen after his talk whether in private scientists on the mission weren’t secretly hoping to detect evidence of past life on Mars. “Like imaging a trilobite?” he joked. It was clear from his presentation, and the MSL website, that this is a mission driven by science and not in the business of setting unrealistic and ultimately self-defeating goals. And yet the rover carries an astonishingly powerful payload of scientific instruments. And the MSL website does nuance things a bit by stating: “MSL does have, however, the capability to detect complex organic molecules in rocks and soils. If present, these might be of biological origin, but could also reflect the influx of carbonaceous meteorites. More indirectly, MSL will have the analytical capability to probe other less unique biosignatures, specifically, the isotopic composition of inorganic and organic carbon in rocks and soils, particular elemental and mineralogical concentrations and abundances, and the attributes of unusual rock textures.” So, while they are not directly looking for the signs of past or present life on Mars, if it pops up they won’t ignore it.
Slopes of Mount Sharp showing that strata at the base of the mountain are relatively flat-lying, whereas higher up they have a steeper inclination. The junction between the two sets of strata (picked out by white dots) appears to be a sharp erosional surface, known as an “unconformity”. Curiosity will be investigating how these differing rock units were formed. (image: NASA)
But for me the most astonishing aspect of Dr Allen’s presentation was the clarity of the images that Curiosity has already taken at Gale Crater. The views were simply breathtaking. This should be no surprise because Curiosity is equipped with a total of seventeen cameras. So while the objectives of MSL may be predominantly scientific, it is already clear that Curiosity is going to bring Mars to life, at least visually, if nothing else. But will Curiosity uncover real evidence for life on Mars? It might not be a mission objective, but it remains a possibility.
The robotic arm of Curiosity examines its first sample (22nd September). (image: NASA)
Curiosity at Gale Crater, an artist’s impression. (image: NASA)