In a development which may untwist a few knickers around the internet, NASA scientists have now explained just what their Phoenix robot lander has found in the soil of Mars - and what the implications are for possible discovery of life on the Red Planet.

Following news that the White House had received secret briefings in advance of any public announcement, internet speculation was rife. Some believed that life - or anyway hospitable conditions for it - had been found. Others said that no, in fact proof positive had been found that Mars could not harbour life, perhaps casting doubt on the value of President Bush's ambitious plans to send a manned mission there.

The truth is somewhat more mundane, according to NASA. Some unusual chemicals, normally seen as poisonous, have been found in the Martian soil at the lander's location. However, according to the NASA boffins, the presence of these perchlorates doesn't mean that life can't exist on Mars.

"Finding perchlorates is neither good nor bad for life, but it does make us reassess how we think about life on Mars," said Michael Hecht from NASA's Jet Propulsion Laboratory - in charge of one of the Phoenix's main dirt-sniffing instruments.

NASA says:

Perchlorates are found naturally on Earth at such places as Chile's hyper-arid Atacama Desert. The compounds are quite stable and do not destroy organic material under normal circumstances. Some microorganisms on Earth are fueled by processes that involve perchlorates, and some plants concentrate the substance. Perchlorates are also used in rocket fuel and fireworks.

So, if we're following this correctly*, there could possibly be Martian animals with perchlorate-fuelled metabolisms, living off perchlorate-concentrating plants. Though there would be a significant risk of these creatures catching fire or exploding if upset - not unlike Terry Pratchett's Discworld dragons, in fact.

On the other hand, you do get the vibe that NASA would really rather not have found perchlorates - indeed would have infinitely preferred it if a little green man had walked up and peered into Phoenix's cameras by now.

More from NASA here. ®

* SCIENCE QUALITY WARNING: The chance that we are following this correctly is roughly equivalent to that of a man with no arms throwing a handful of jelly through a falling doughnut at fifty yards without touching the sides.