A PASSION FOR SPACE
The Curiosity rover has been on Mars over 2,000 sols now but its biggest revelations may be still to come
Sitting atop the Vera Rubin Ridge in Gale crater, Curiosity rover has just celebrated two major milestones. It has now been exploring the Red Planet for 2,000 sols – or Martian days – having traversed 18.7km since August 2012. Which also means it’s been on the planet for three Martian years.
From this vantage point, Curiosity’s science team has enjoyed some remarkable panoramic images thanks to the rover’s Mastcam cameras. For those of us familiar with deserts from fieldwork, they have a weird Earthly quality, with hills and mountain slopes of stratified sedimentary rocks that resemble what you might find in North Africa. But scattered here and there are those tell-tale signatures of a different world: impact craters, holes gouged into the surface by colliding meteorites.
Curiosity’s mission to Mars is first and foremost an exploration of habitability; to assess the Martian surface as a potential habitat for past or present life. Our focus is the ancient rock successions preserved in Gale crater that hail back to a time when Mars’s climate may have been more hospitable to microbial life than today’s harsh conditions. This is where my own speciality comes into play.
Written in the rocks
I am a sedimentary geologist. Through clues in rocks, I can tell you what a landscape looked like millions, if not billions, of years ago. But I never imagined I would be doing this on Mars.
Curiosity’s travels in Gale crater have revealed a spectacular array of sedimentary rocks which attest to dynamic ancient environments. Rivers derived from the crater rim built alluvial fans composed of rounded pebble beds and small underwater dunes. These rivers eventually built a series of deltas that fed water and sediment into a lake that the science team believes filled the centre of the crater. Lake deposits are brilliant for astrobiology. They not only represent quiet-water environments with good potential for the development of microbial life, but they also increase the chances of preserved evidence.
Preservation is a crucial factor. Life may have been present, but its traces erased by billions of years on the surface of Mars. In Gale crater we found remarkable mudstones made up of millimetre-thick layers – laminations – that record the settling of fine-grained sediment in a standing body of water. We’ve driven across hundreds of metres of such laminated mudstones, which suggests that this lake existed for hundreds of thousands, if not millions, of years.
The rocks that make up the Vera Rubin Ridge are also finely laminated mudstones but with an abundance of the iron oxide, haematite. We knew about the haematite from orbital observations, but not how it came to be. Was it related to the chemistry of the lake water? Was it caused later by fluids percolating through the rocks? And what implications does it have for possible life on ancient Mars? The Curiosity science team is grappling with these problems at this very minute. Watch this space!
Dr Sanjeev Gupta is a co-investigator on the Curiosity rover’s Mastcam team
Maggie Aderin-Pocock is on holiday
The Vera Rubin Ridge looks deceptively Earth-like, but its remarkable rocks have a hidden tale to tell
Martian mudstones found at the base of Mount Sharp in Gale crater