Nasa images show signs of recent flowing water on Mars
"Perhaps there could be hardy microbes surviving in these short periods of summer meltwater on the desert surface of Mars."
- Dr Lewis Dartnell, astrobiologist at University College London
Striking new images from the mountains of Mars may be the best evidence yet of flowing, liquid water, an essential ingredient for life.
The findings, reported today in the journal Science, come from a joint US-Swiss study.
A sequence of images from the Mars Reconnaissance Orbiter show many long, dark "tendrils" a few metres wide.
They emerge between rocky outcrops and flow hundreds of metres down steep slopes towards the plains below.
They appear on hillsides warmed by the summer sun, flow around obstacles and sometimes split or merge, but when winter returns, the tendrils fade away.
This suggests that they are made of thawing mud, say the researchers.