“Today, the wheels of Curiosity have begun to blaze the trail for human footprints on Mars. Curiosity, the most sophisticated rover ever built, is now on the surface of the Red Planet, where it will seek to answer age-old questions about whether life ever existed on Mars -- or if the planet can sustain life in the future.”— NASA Administrator Charles Bolden (5th August 2012)
NASA’s Curiosity rover trundling around on the Martian surface is a stark reminder of how much there still is to learn about the red planet. It might be a phenomenal display of technological prowess, with detachable heat-shields, parachutes, sky cranes and jet thrusters, but the reason for the journey is our own ignorance. Travelling to Mars has long since been a dream for mankind, and the latest rover hopes to bring us ever closer to answering some of the persistent questions regarding the red planet.
Is there or has there ever been life on Mars?
If life exists anywhere else in our solar system, Mars is one of the prime contenders. People all over the world are desperate to find out if life exists elsewhere in the universe. Although it’s one of the main interests of people learning about the Curiosity rover, scientists have to be much more realistic about it. John Grotzinger, a lead scientist on the mission, confirmed that “Curiosity is not a life mission. What we are doing in this mission is exploring for habitable environments.” Habitable environments don’t prove there was or is life, but that it could feasibly exist or have existed on the planet. They aren’t expecting complex, intelligent creatures living in underground metropolises, but possibly evidence of past microbial organisms.
The most tantalising reading ever recorded which relates to life on Mars was taken by Viking. This was the first spacecraft to ever land on the Martian surface, and it detected something very unusual on its hunt for life. Methyl chloride and dichloromethane were found on the surface, which we know on earth as organic (life-related) chemicals. The readings were eventually blamed on contamination from cleaning fluids from earth, but the ripples they created can still be felt. 36 years after Viking landed on Mars, Curiosity set off to investigate the same issue.
Despite all of this interest and exploratory effort, the chances of finding life on Mars now seem slim. The planet is arid, quite cold and also pretty radioactive. The earth’s magnetic field protects us from the consistent “solar wind” of charged particles, but Mars’ magnetic field disappeared around 500 million years after the planet’s formation. The reasons for this are unclear, but the leading theory is that a series of sizeable asteroid impacts upset the temperature balance required for convection (how planets generate a magnetic field). Today’s Mars is likely devoid of life because it lacks this magnetic shield, but the planet’s more hospitable historical atmosphere might have allowed life to flourish.
Is there still water on Mars?
The quest for life is increasingly tied in with the quest for water. The reasons for this are pretty straightforward: life requires complex chemistry and water is the most abundant effective “solvent” (which allows other chemicals to be dissolved in it) in the universe. Carbon and the other elements required for life are given a perfect place to combine in liquid water. Some scientists believe that Mars was once warm enough for water to exist on the surface (in at least some places), which indicates that life could have existed on the planet.
There is abundant evidence for the previous existence of water on Mars. Viking found significant amounts of water in the planet’s soil and apparent river deltas, valleys and ocean beds have been identified on the surface. The Martian surface also holds many minerals which require water to form, which adds further weight to the idea. It’s thought to still exist deep underground and possibly for fleeting moments on the surface. The dismal atmospheric pressure would prevent it from lasting very long, but track-marks have been observed on a slope in one of Mars’ craters that could suggest a spring-time salt water flow.
By analysing the layers of rock embedded into Mount Sharp, Curiosity will provide scientists with an environmental history of Mars. Not only will this deepen our understanding of the planet’s past, it should give scientists an idea of when life would have been possible on Mars and help them identify possible previously habitable areas to focus on in future searches.
Founder and president of the Mars Society, Robert Zubrin, summed up the importance of water for life on Mars by stating that “If one thinks the laws of science of life on Earth are the same elsewhere in the universe — which I do — then it's rational to believe that life once developed on Mars when it was a warm and wet planet. There may now be fossils on the surface and maybe living organisms underground.”
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