Now that Philae has woken up, we may be on the brink of major steps forward in our understanding of comets. We already know that perhaps as much as 30% of a comet consists of dust and organics. Now we'll be able to look at this close up. Why, though, do most scientists expect Philae to find pre-biotic chemistry? Is there any chance of life? Also, where else in the solar system can we look?

The ancient oceans of Jupiter's Europa and Saturn's tiny Enceladus are hidden beneath an ice sheet kilometers thick. They may have ET microbes, even multicellular swimming creatures around hydrothermal vents. Or they could have imperfectly reproducing "protocells"; a window into the first stages of evolution. 

These conditions, which make them so habitable, and interesting for astrobiology, may also make them especially vulnerable to invasive species. Cassini orbiter found geysers at the south pole of Enceladus, continually venting sea water from its ocean into space, as ice particles. This may give us a wonderful opportunity to look at ET life in our solar system without interference from Earth life.

If an extraterrestrial race - or indeed later civilization on the Earth looks at the relics of our space explorations - one thing they might notice is our fondness for placing flags and pennants in space. All the space faring nations have signed the Outer Space Treaty. So these are not claims of territory (forbidden by the treaty) but rather, celebrations of national pride and accomplishment.

Elon Musk, and NASA both have in mind the idea of doing interplanetary voyages straight away, aiming for Mars, with Obama going so far as to say about the Moon: “But I just have to say pretty bluntly here: We’ve been there before.”. If you hold that view, you are undoubtedly in distinguished company.

Now - there are two things here - yes we've been to the Moon before - but is that the end of all interest in it? But first - how ready are we for interplanetary voyages? 

The present day habitability of Mars is an area of research that has exploded hugely in the last decade, to the extent that it's often hard to keep track of everything that's going on. This is by way of background material for my other articles on habitability of Mars.

I've talked before about how life on present day Mars could be vulnerable to Earth life. If only humans could be sterilized of other life, like a plant seed. But sadly, we can't do that, and it would kill us to try. Recent ideas, and experiments in Mars simulation chambers suggest that there may be liquid water habitats on the surface of Mars. They may be no more than droplets of water a few millimeters in diameter, but these still are, as Nilton Renno said, "Swimming pools for a microbe".