How has Mars changed over billions of years?

Mars, our rusty, red neighbour, has long since been a source of fascination for star-gazers, scientists and science fiction fans. This world has sparked the imaginations of many in the hunt for alien life and it may even become a potential astronaut destination in the future. Many robotic rovers have helped us understand more and we know this planet now to be a dry desert-like planet, but was it always like this?

Any water on Mars is locked up in the ice caps. (Image Credit: Image Credit: NASA/JPL-Caltech/MSSS.)

The most recent successful mission to Mars is the Mars Science Laboratory better known as the Curiosity rover. It arrived onto the Red Planet in August 2012. The rover has already been exploring an area of Mars, 95 miles (150 km) wide, the Gale Crater, after its successful landing just to the crater’s north. Curiosity’s primary role is to search for conditions that may have once been able to harbour any sort of bacterial life concealed beneath the Martian surface. It is also acting as a weather station, can also measure radiation levels as well as taking high resolution pictures and videos.  As well as investigating the Martian environment, Curiosity’s discoveries will also help in the planning and implementing of future human missions to the red sphere.

Curiosity Rover’s selfie at the ‘John Klein’ Drilling Site. ( Image Credit: NASA/JPL-Caltech/MSSS.)

Mars is red because it has rusted and one of the main causes of rust here on Earth is water. Mars also has gullies and markings which suggest that water has carved its path across the planet. However any water has since evaporated off the surface because of the thin atmosphere, any remaining water is locked frozen inside the ice-caps. No large bodies of water currently exist on Mars. However, the rovers that have been exploring Mars have found traces of water not on the surface but buried beneath.  Rocks dislodged by impacts or eroded away by the weather and wind reveal a different chemical composition than surface rocks, suggesting sub-surface water existed. Using what we know about life on Earth, where there is water, there is life, signs of water may help us understand what Mars was like billions of years ago.

John Klein drill hole, the sample taken from here reveals an interesting wet past. (Image credit: NASA/JPL-Caltech/MSSS)

Curiosity also has the ability to drill beneath the surface, as well as having instruments able to investigate the samples revealed.   The rover can then analyse the findings to reveal more about the landscape. Curiosity used its drill for the first time in February of last year, drilling into the ‘John Klein’ rock at the Yellowknife Bay area in Gale Crater. Curiosity’s debut drilling at the site, named after a deputy principal investigator on the mission, was the final proof that all instruments were working correctly. The drilling process is a slow one perhaps taking a couple of days. Soil samples from the different layers of Mars are all analysed in the hopes of ground-breaking discoveries.

Image- Sheepbed lake? (Image credit: NASA/JPL-Caltech/MSSS)

Samples taken in February have revealed that this area of Mars was once covered in a large freshwater lake. The drill hole is part of the Sheepbed mudstone and the soil grain here is very fine. Surfaces like Sheepbed have only been revealed due to wind erosion and may only have seen daylight as recently as 70 million years ago.  Curiosity discovered that the samples taken from beneath the surface contained minerals suggesting that bacterial life may have been able to survive here and the samples reveal this surface to be rich in clay deposits as well as having a neutral PH. Rock-eating microbes similar to examples found on Earth may well have been able to thrive within the lake with these conditions. The rocks at Gale crater are thought to be 4.2 billion years old. However the lake may have existed as recently as 3.5 billion years ago, and the research suggests that the lake was not some brief feature but may have lasted longer and may have had rivers and ground water.  Previous information sent in the past from the Spirit and Opportunity rovers suggested that any water on Mars may have been acidic but this latest discovery proposes that this ancient lake water may even have been drinkable.

Launch of MAVEN in November 2013. This spacecraft is searching for clues to reveal what happened to the Martian atmosphere. (Image credit: NASA)

Billions of years ago, Mars could have enjoyed a much wetter climate with the possibility of supporting life. The Curiosity rover, despite, discovering fresh water once existed, cannot tell if that definitely means life did exist. Perhaps in the next few decades if a sample return rover were to exist it may give more insight into potential life on Mars. Even the MAVEN (the Mars Atmosphere and Volatile EvolutioN) spacecraft on route to Mars at the minute should towards the end of 2014 start to give us an insight in the Martian atmosphere or lack thereof, and provide a valuable look into the evolution of Mars from a wet world to a desert planet.

Curiosity and the other Martian rovers have only explored a fraction of the planet. If the rovers are able to map a much larger surface area, perhaps more traces of water or even life may be found. Curiosity is currently making a nine month trip to the base of Mount Sharp, the central peak at the centre of Gale crater in order to discover more about the red planet. Perhaps 2014 will bring some exciting new findings!

Should Curiosity ever find life, I’ll be there, part of history! ( Image credit: Martina Redpath)

(Article by Martina Redpath, Education Support Officer)