Results are in from Messenger, the spacecraft that swooshed past Mercury in January. To my great disappointment there’s no mercury mentioned in the results.

This is mankind’s second visit to the planet, after the Mariner 10 mission popped in on Mercury in 1975. Scientists noted then – and during the Apollo16 moon mission three years earlier – that the planet hosts some unusually flat plains. Scientists have been debating ever since whether they were formed by vulcanism or by a big whalloping impact.

The mission’s aim was to work out why Mercury was so smooth, and what created its magnetic field (but not to find out if there was any mercury there). The answer: volcanoes created the plains, and the planet’s ever-decreasing liquid, iron-rich core produces the magnetic field.

As published in 11 papers in Science this week, other news from the planet is that it is shrinking, and it has had a violent, volcanic past.

In addition they discovered that the atmosphere there contains ions of sodium, oxygen, sulphur, hydrogen sulphide, silicon and (“astonishingly”) water ions – but no notable amounts of mercury.**

** OK, I never really thought that Mercury was a huge ball of shimmery, slippery mercury. But that story about the Moon being made of cheese – now that’s a winner…

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington