“We think that Mars used to have a magnetic field,” explains Bruce Jakosky, the Principal Investigator for Maven, who is based at the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. “We see places on the surface that retain some remnant magnetism, they were imprinted when they formed with whatever magnetism was there. We think that some four billion years ago, when the magnetic field turned off, that turn-off of the magnetic field allowed turn-on of the stripping by the solar wind.”
To investigate the processes taking place today, Maven will dip into the tenuous Martian upper atmosphere with each orbit, measuring the particles, sampling gases, monitoring the magnetic field and solar wind. “Rover missions for the past fifteen years have focused on habitability and the history of habitability,” says Jakosky. “We’re trying to get the other half of the problem, what role the top of the atmosphere has played. The rovers get the bottom of the atmosphere, we get the top of the atmosphere and how it interacts with the Sun.” Both are needed to put together a picture of what’s controlling the Mars environment. Results from the Curiosity rover published in Science last week, for instance, supports the evidence that Mars may have lost most of its atmosphere billions of years ago.
As well as filling in the blanks about Mars' depleted atmosphere, Maven will also provide clues to the habitability of other planets, beyond the solar system. “In trying to understand the distribution of life throughout the Universe, this is a really important indicator,” says Jakosky. “Understanding the environmental conditions that allow [life] to exist, or don’t allow it to exist, is key to being able to extrapolate elsewhere.”
Right now, Mars is being studied in unprecedented detail – from spacecraft in orbit and by rovers on the ground. Maven will provide another part of the jigsaw as we build up an understanding of a planet that, it is now becoming clear, used to be remarkably like our own.
“Imagine that!” exclaims Beutelschies. “We had a solar system with two planets with oceans on them! That certainly raises the question in many people’s minds about whether Mars could have had life sometime in the past.”
For Mars it, somehow, all went horribly wrong. We should just count ourselves lucky we evolved on Earth instead.