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 arrive when humans colonise it.
Scientists analysing soil lifted from the surface of the planet, by the Nasa space probe Phoenix, have admitted to being "flabbergasted" by results which suggest it would theoretically be ideal for vegetables that thrive in mildly alkaline conditions.
The one cubic-centimetre soil sample 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. "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.
"There is the type of soil you'd probably have in your back yard."
The sample's pH level was between 8 and 9, with 7 considered neutral. This does not mean that dropping seeds would produce a vegetable patch, given everything else about Mars' environment, including the lack of water.
However, in an earlier experiment, soil was heated on board the lander to 982C, resulting in the release of water vapour. This suggests that part of the planet was in contact with water at some point.
Other minerals found in the sample were magnesium, sodium, potassium and chloride ions, making it similar to soil found in Antarctica.
Phoenix set down on the planet last month.