Cape Town - We might all have been living on Mars – or at least, some sort of creatures a bit like us could have been living there.
That’s because when the planets of our solar system were still young, a few billion years ago, Mars was also a “Goldilocks” planet not unlike Earth – not too hot, not too cold, and with plenty of life-supporting water in liquid form flowing in rivers and emptying into lakes and shallow seas.
A thick atmosphere of carbon dioxide blanketed Mars and kept it warm, creating conditions where microbes may have thrived as they did on Earth.
But that’s not how things continued there, says Dr Tony Phillips, the production editor of the US space agency’s on-line news service, Science@NASA.
“Today, Mars is bitter cold and desiccated. The planet’s thin, wispy atmosphere provides scant cover for a surface marked by dry riverbeds and empty lakes. If Martian microbes still exist, they’re probably eking out a meagre existence somewhere beneath the dusty Martian soil.”
What changed on Mars has long puzzled scientists, and now Nasa is sending a new spacecraft to Mars called Maven (Mars Atmosphere and Volatile Evolution) to find the answer. Scheduled for launch later this month and due to arrive at the Red Planet next in September, the orbiter is packed with instruments to study Mars’s upper atmosphere.
“That’s where many researchers believe the answer lies. The only way Mars could have been wet and warm 4 billion years ago was if it also had a thick atmosphere,” says Phillips.
“Carbon dioxide in the Martian atmosphere is a greenhouse gas, just as it is in our own atmosphere. A thick blanket of CO2 and other greenhouse gases would have provided the warmer temperatures and greater atmospheric pressure required to keep liquid water from freezing solid or boiling away.”
But something caused Mars to lose that blanket, says Phillips.
“One possibility is the solar wind. Unlike Earth, Mars is not protected by a global magnetic field.”
Maven will be the first mission to Mars specifically designed to help scientists understand the ongoing escape of CO2 and other gases into space, and the probe will orbit the planet for at least one Earth year.
Once scientists know how quickly Mars is losing CO2 now, they can extrapolate the total amount lost over the past 4 billion years, says Phillips.
“In the grand scheme of the solar system, Earth orbits alongside a world that began with as much promise for life as our own, yet turned out so differently.
“After all these years, Maven could write the final chapter in a haunting planetary mystery.” – Cape Argus