The Geek Chronicles, Chapters 1 and 2

Chapter 1

Enough water is locked up at Mars' south pole to cover the planet in a liquid layer 11m (36ft) deep.

The Mars Express probe used its radar instrument to map the thickness of Mars' south polar layered deposits.

Analysis of the Marsis radar data shows that the polar deposits consist of almost pure water-ice. ...

Based upon data from the Mariner and Viking projects, the polar layered deposits were considered to be accumulations of dust and ice.

The new information says that the mixture is actually 90% ice and 10% dust. It's now known that areas of Mars were once wet, raising the possiblity that there once was life there and, in the more speculative scenarios, may still exist there - although no one expects such life to be of a more complex level than microbes. But, even assuming there is still some source of water beyond the poles, even existing as frost mixed in the soil, where could such life exist in the harsh climate that is Mars? A perfect lead-in to

Chapter 2

Scientists studying pictures from Nasa's Odyssey spacecraft have spotted what they think may be seven caves on the surface of Mars.

The candidate caves are on the flanks of the Arsia Mons volcano and are of sufficient depth their floors mostly cannot be seen through the opening. ...

The authors say that the possible discovery of caves on the Red Planet is significant.

The caves may be the only natural structures capable of protecting primitive life forms from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface.

The cave entrances are wide - between 100 and 252 meters (330-828 feet) - and the caves themselves, which appear to have roughly vertical sides, are a minimum of 73 to 96 meters (240-315 feet) deep; observers can't tell for sure because in most cases they can't see the bottom. In the one case they can, the cave is at least 130 meters (436 feet) deep.

And by the way: Mars rovers Spirit and Opportunity are now on Day 1141 and Day 1120, respectively, of their 90-day missions.