ExoMars is a challenging, difficult but tremendously important project if we ever want to have a robotic exploration programme in our neighbourhood in the Solar System.

BBC: Esa-Nasa Mars missions' race against clock

At present, British government policy specifically bars any public programmes connected with human spaceflight, and it has directed that any monies instead go towards the robotic exploration of space - for example in Earth observation and unmanned planetary probes.

BBC: RELATED BBC SITES

Here's the second critical point: Don't forget robotic space exploration, the other half of what NASA does.

CNN: Space is still the new frontier

Better, say the doubters, to spend the money on scientific missions, such as Hubble's successors, and leave exploration to the kind of robotic missions that have successfully roved about on the surfaces of Mars and Titan, one of Saturn's moons.

ECONOMIST: The space shuttle

This unlikely sounding collaboration is taking place between researchers interested in exploring Lake Vostok in Antarctica, which is sealed off below several kilometres of ice, and planetary scientists, who see such exploration as a possible dress rehearsal for a future robotic mission to Jupiter's moon Europa, whose icy surface is thought to conceal vast oceans that might harbour extraterrestrial life.

ECONOMIST: Planetary pretenders

Further exploration, he said, with the Deepsea Challenger and other robotic vessels would be the only way to find the answers.

BBC: Science & Environment

Beginning no later than 2008, we will send a series of robotic missions to the lunar surface to research and prepare for future human exploration.

CNN: Bush: 'It is time for America to take the next steps' in space

While manned exploration had until now seen a 52-year hiatus, scientists have used two robotic unmanned vehicles to explore the Mariana Trench: Japan's Kaiko made a dive there in 1995 and the US-based Woods Hole Oceanographic Institution's vessel Nereus explored the deep in 2008.

BBC: James Cameron back on surface after deepest ocean dive