Martian soil 'good enough for asparagus'

(Nasa/JPL)

Bad for strawberries, great for asparagus and turnips. This is the small-print for gardening enthusiasts buying a second home on Mars, should the day ever arrive when humans colonise it.

Scientists in charge of analysing soil lifted from the surface of the planet by the Nasa space probe Phoenix have admitted to being “flabbergasted” by initial results, which suggest it would theoretically be just about perfect for certain vegetables that thrive in mildly alkaline conditions.

The tiny sample of soil – one cubic-centimetre – was lifted from the planet’s surface with a robotic arm. It was then mixed with water on board the lander to create a kind of Martian mud suitable for chemical analysis. Phoenix set down on the planet last month.

Most scientists had long assumed there would be little on the surface of the planet that would be hospitable to supporting life. But last week they were forced to change their thinking.

“We have found what appear to be the requirements, the nutrients, to support life whether past, present or future,” said Samuel Kounaves of Tufts University near Boston. “The sort of soil you have there is the type of soil you’d probably have in your back yard.”

The pH level of the sample was somewhere between 8 and 9, with 7 considered neutral. This would seem perfect for growing asparagus and other vegetables, such as green beans, that do not do well with acidity. This does not mean that dropping seeds now would produce a vegetable patch, given everything else about the planet’s environment, including, of course, the lack of water.

Even the water question has been the subject of excitement since Phoenix began its work. In an earlier experiment, soil was heated on board the lander to 1,800F, which resulted in the release of water vapour. This suggests that this part of the planet at least was in contact with water at some point, although nobody can say when that was or the volume of water involved.

“This soil clearly has interacted with water in the past,” said William Boynton, of the University of Arizona, who led the water content experiment. He added that it could have come in dust particles blown from a different part of the planet.

But it was the vision of potted asparagus in Martian mud that was commanding the widest attention. “We’re flabbergasted by this data,” Dr Kounaves said. “There’s nothing about it that would preclude life. In fact, it seems very friendly.”

Other minerals found in the sample were magnesium, sodium, potassium and chloride ions, making it similar to soil found in Antarctica.