Life on Mars? Curiosity drops in to find out
Finding out whether life can exist on other planets has been one of the hopes of scientists since we first sent radio signals into the sky. In the early hours of Monday morning, the world’s most advanced planetary rover will begin work on what is likely to be our best chance yet of answering that question.
I was asked the other day whether Curiosity, the NASA rover rapidly approaching the Red Planet, will finally provide a breakthrough to end the decades-long search for Martian life, but, of course, science doesn’t always work like that. We’re not likely to suddenly find fossils that give us an instant answer. Instead, NASA scientists will use a complex set of technologies to build up a picture of the conditions that existed on Mars millions of years ago and use this to determine whether the planet could have supported life.
Curiosity essentially carries a very advanced chemistry set (hence the mission name Mars Science Laboratory) that will allow it to gather much more detailed evidence than ever before. This includes: an array of cameras and other imaging devices; radiation, atmospheric and environmental sensors; and mass, X-ray and laser spectrometers.
The scientists analysing the data that comes back include two British researchers funded by the UK Space Agency. Dr John Bridges from Leicester University will be among those studying the composition of Martian sediments thought to be clay (and therefore created with water) collected by the rover.
‘Once we know accurately what was there,’ he explained, ‘we can then do a bit of modelling and work out what the temperature was, and was it acid or alkaline, and what the composition of the fluid was – was it poisonous for microbial life or was it just the sort of thing they like to live in?’
The key to doing this will be the instruments on board Curiosity, which are more sophisticated than any previously sent to Mars and can detect much smaller traces of a wider range of compounds. ‘Even on Earth this would be a powerful chemistry lab but we’re sending it to Mars,’ said Bridges.
First are the cameras that can capture high-resolution colour images and video (at 10 frames a second), including monochromatic images for studying light absorption at different wavelengths, all stored and processed by the cameras’ internal electronics systems.
There’s also a sophisticated version of a geologist’s hand lens – the Mars Hand Lens Imager (MAHLI) – to provide close-up views of the minerals, textures, and structures in Martian rocks. The self-focusing, 4-cm-wide camera can take colour images of features as small as 12.5 micrometers and use UV light to reveal any carbonate minerals or those created by evaporation of water.
To get an even more detailed picture of what’s inside the rocks, a range of spectrometers will bombard the mineral samples with different types of energy and use the pattern of energy returned to work exactly what elements and compounds are present.
The Alpha Particle X-Ray Spectrometer (APXS) will measure the X-rays produced when materials are hit with radioactive alpha particles produced by a curium source, enabling scientists to measure the abundance of rock-forming elements. A second device, the Chemistry and Mineralogy instrument (CheMin) works by firing X-rays at a sample and measuring their angle of diffraction to identify the crystalline structure of materials.
ChemCam will use a remote micro-imager to analyse the composition of plasma (ionised gas) formed by vaporising rock samples smaller than 1mm in diameter with a laser. While the APXS works best when touching the rock surface, ChemCam can operate from up to 7m away to identify rapidly identify how the rock was formed, measure the abundance of elements, recognise ice and minerals containing water molecules and measure weathering rinds on rocks.
A final instrument suite, Sample Analysis at Mars (SAM), will make up more than half the science payload of the rover. This will search for elements associated with life, such as carbon, hydrogen and oxygen, by separating soil compounds with a mass spectrometer, by vaporising rocks and analysing the resultant gas using a gas chromograph, and by studying the atmosphere with a laser spectrometer.
All this work should begin relatively quickly once the rover has made its way to a mountain of sediment in the middle of a giant crater. But first it has to land safely and the car-like size of the rover and its 900kg mass mean this isn’t easy. It is too heavy to use giant airbags to cushion its fall as previous rovers have. Instead NASA has developed a novel system know as SkyCrane.
After using small precision landing rockets to guide the landing vehicle to within 20km (12 miles) of its target site, a huge parachute – 10 per cent bigger than any used before – will deploy and start to slow the descent. Once the heatshield has been discarded, reverse rockets at the base of the lander will help slow the vehicle further and stabilise it from horizontal winds.
Then comes the SkyCrane technique – an “umbilical cord of cables will lower the rover away from the landing vehicle towards the ground, enabling it to move off from the landing site as soon as the cord disengages. Once this happens, the lander’s rockets will then direct it away from the rover below, powering away for a crash-landing far from Curiosity.
SkyCrane on its own is a fantastic testament to human engineering and creativity, and it’s hard to imagine how high the tension will be in mission control at 6:00AM (BST) on Monday when Curiosity finally touches down. Due to the time it takes for communications to reach Earth from Mars (14 minutes), the team won’t even know if the landing has begun successfully until well after the rover is either safe on the ground or disaster has struck.
But the rover itself will be embarking on an even more amazing journey. Using some of the most advanced tools science has managed to create, Curiosity will act as the world’s greatest detective in an attempt to piece together a picture that could answer one of humanity’s most fundamental questions.