The latest Martian Rover ‘Mars Science Laboratory’/Curiosity (Fig. 1) landed in August 2012 in Gale Crater on Mars, and has already travelled 1.7 km. One of its main goals is to determine whether Mars could have sustained favourable conditions for microbial life by investigating in-situ information on climate and geology. Gale Crater was chosen because of its water-deposited sediments (alluvial fan – see Fig. 2) and its central mountain Aeolis Mons that exposes 2 billion years of sedimentary records. In the past two years, the famous Rover dated a rock, gave insight of surface radiation, highlighted how erosion reveals the building blocks of life and gave evidence that the Red Planet once had a suitable environment for microbial life.
Thanks to MSL/Curiosity, scientists have succeeded in measuring how long an outcrop in Gale Crater has been exposed by wind-blown erosion. Specific gases are produced by cosmic rays when they hit atoms of rock on the surface and these are analysed by the laser on the Rover’s head. They revealed a very young exposure (relative to Mars!) of only 60 to 100 million years. This is very important information because the younger an outcrop (i.e. the less time it has been exposed for), the more it may exhibit preserved organic chemicals.
The first rock drilled by MSL/Curiosity, named ‘John Klein’ and located in a lake-bed area (i.e. rich in clay minerals – a key chemical component for life), revealed that the water was not too acidic or too salty and was composed of a mix of sulfur and iron-containing minerals. This mix is used on Earth by rock-eating microbes as a source of energy similar to two poles of a battery exchanging electrons. Moreover, the particular clay minerals of the area, the ones that would really stick to your boots (called smectite), are extremely biologically rich environments on Earth.
The second rock drilled, named ‘Cumberland’ (Fig. 3), is the first ever extraterrestrial rock to be dated from in-situ analysis of minerals. It was estimated to be 3.86 to 4.46 billion years old (Martian period of the Noachian), which confirms the previous estimation of rock ages in Gale Crater. But investigation of mineral abundance in the ‘John Klein’ area revealed that clays were formed in upstream sources and were deposited later in Gale Crater during the next Martian period.
Consequently, scientists have concluded that a suitable environment for microbial life existed in the relatively not so distant past, during the Martian period of the Hesperian from 3.7 to 3 billion years ago – a period during which pond of water were becoming acidic and briny. Interestingly, this is also approximately the same period of the oldest trace of life on Earth. Moreover, scientists have also suggested that those habitable conditions on Mars were stable for millions of years.
In two years, the main goal of MSL/Curiosity was completed: we now know that a suitable environment for microbial life existed on Mars for billions of years – but not life! Indeed, the mission has not yet ended and evidence of life still needs to be investigated on the Red Planet. In addition, the Rover is helping to prepare for future human missions on Mars by collecting data on the amount of radiation received on the surface as well as continuing to provide beautiful images of the Martian landscape…
- See the interactive billion-pixel view from MSL/Curiosity at: http://mars.nasa.gov/multimedia/interactives/billionpixel/
- See also this news release from NASA’s Jet Propulsion Laboratory.