7 Fascinating Facts about Mercury, and the joint ESA/JAXA BepiColombo mission, with planetary scientist and space weather expert Suzie Imber. It’s a bite-sized version of her brilliant talk at Space Rocks London 2019!


1. Mercury is incredibly dense compared to the other rocky planets

“Mercury’s density tells us that it contains a large amount of metal – as opposed to rock – with a massive metal core. Did it used to have an outer rock core outside that got blasted away? Or did it form in the way we see it today? We have no idea what the answer is!”








2. Mercury’s magnetosphere is much smaller and weaker than that of the Earth

“A magnetosphere is the region of space dominated by the magnetic field of a planet.  Mercury is a small planet that spins very slowly, so it has a very weak magnetic field and a very small magnetosphere, which gets constantly pummelled by solar explosions.’





3. Mercury is the closest planet to the Sun, and gets roasted, with temperatures reaching up to 450°C

But on the other side facing away from the sun, the temperature is about -180°C. This is because Mercury has no atmosphere and rotates very slowly (so slowly in fact that one day on Mercury is equal to almost two months on Earth), thus cannot sustain a more stable global temperature.”




4. Mercury’s surface is covered in holes, and even has wrinkles!

“Mercury’s crust is covered by impact craters, like on the moon. They were formed around 4 billion years ago by a bombardment of rocks. It has unique features called lobate scarps – or ‘wrinkle ridges’. We think Mercury was so hot when it was formed and has been cooling ever since that it shrank as it cooled and has shrunk so much its ‘skin’ ended up too big for it!”

• Click/pinch/zoom/swipe the above image to explore Mercury’s surface. 


5. The BepiColombo mission has a camera design based on the eye of a lobster

“My university (the University of Leicester) built the MIXS (Mercury Imaging X-ray Spectrometer) instrument which is on board the European Mercury Planetary Orbiter, part of the BepiColombo mission. It is designed to tell us about Mercury’s surface by measuring its elements and so we can make composition maps. The camera has an incredibly high pixel resolution so that we can look at really small-scale features to see what they’re made of. The technology that was used to create an image with pixels is based on how a lobster eye works!”


6. Craters on Mercury’s surface contain unexplained mysterious ‘hollows’

“Inside the surface craters are more holes – but not regular circular holes – called hollows. We don’t know what causes them. We think escaping volatiles (gases) could be causing their formation – nobody really knows. We hope that with MIXS we can measure the composition of the surrounding materials which might give us a clue.”





7. The dark, night side of Mercury is a source of mysterious x-rays!

“X-rays emitted by a planet are caused by sunlight hitting its surface. Therefore, no x-rays should be given off by the night side of Mercury. We just happened to be plotting some data and discovered the x-rays, so we delved deeper. On Earth we have the Aurora Borealis (Northern Lights) and Aurora Australis which are caused by the interaction of the sun with the Earth’s magnetosphere: particles are accelerated and hit the Earth’s atmosphere causing the glowing lights. We realised the same process was happening on Mercury, but the particles were instead just ploughing into the planet’s surface – because there is no atmosphere – and giving off x-rays. So we discovered Mercury’s X-ray Aurora, which is good fortune because we happened to have just built our MIXS instrument to go to Mercury to study X-rays!”



Thanks to Suzie Imber. You can follow Suzie on Twitter and you can find out more about BepiColombo here.





Picture credits

Mercury surface animation: NASA Visualization Technology Applications and Development (VTAD)

Mercury Imaging X-ray Spectrometer: University of Leicester

Mercury hollows: NASA / JHUAPL / CIW