As planets go, Mercury is a world of extremes 鈥� and one that doesn鈥檛 always make a great deal of sense. Its iron core is absurdly and inexplicably huge. Despite its searing temperature, it has ice trapped at its poles. It is also pummelled every day by wild solar storms 鈥� the likes of which Earth only experiences once a century.
Suzie Imber hopes she can help us get to know the planet a little better through her work as a co-investigator with Europe and Japan鈥檚 BepiColombo mission, which last week made its final and closest flyby of Mercury, helping it to slow down before it enters orbit in 2026. Imber, based at the University of Leicester, UK, is an expert on space weather and says her studies of Mercury could help us prepare for the worst solar storms here on Earth. She was also, in 2017, the winner of the BBC鈥檚 Astronauts: Do you have what it takes?, a gauntlet that pitted contestants against the rigours of space travel.
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Imber told New 杏吧原创 why she is so excited about sending a mission to Mercury, what we hope to learn about this intriguing planet and whether she might one day venture out to the final frontier herself.
Jonathan O鈥機allaghan: Why are we returning to Mercury now?
Suzie Imber: There are loads of reasons. From a high-level perspective, it鈥檚 a pretty unexplored planet. We鈥檝e had three flybys and one orbital mission 鈥� NASA鈥檚 MESSENGER, which orbited between 2011 and 2015 鈥� but the more we learn, the more questions come up. We think there鈥檚 water ice deep in the permanently shadowed craters near the poles, but we don鈥檛 know how it鈥檚 still there. There seem to be some mystery substances called low-reflectance materials covering this ice; these appear to be carbon-based, but we don鈥檛 fully understand them. It鈥檚 also the only planet we know of that we think has contracted considerably.
You鈥檙e saying Mercury has shrunk? Tell me more鈥�
The MESSENGER mission discovered these interesting surface features called lobate scarps and that we don鈥檛 see anywhere else. We think they formed as the planet鈥檚 surface contracted in size, creating this bunching up of the surface rock. As far as we know, Mercury contracted in diameter. It doesn鈥檛 sound like much for a planet nearly 5000 kilometres across, but it鈥檚 quite considerable.
Your own particular interest is in space weather. Why is Mercury so fascinating from that perspective?
When we talk about space weather, we mean the 鈥渨ind鈥� of particles and magnetic fields streaming from the sun that washes over the planets. On Earth, if the conditions are right, this can cause problems with electrical systems. The worst-case space weather scenarios that we see on Earth 鈥� which can damage satellites and knock out power grids 鈥� happen once a century. But on Mercury you get extremely powerful solar storms every day. We鈥檙e still trying to figure out what that does to the planet. It has a weak magnetic field, and it鈥檚 very close to the sun. Is there a direct, observable effect on the surface? We鈥檙e interested in whether that could be the case. And if you鈥檙e wondering, by the way, there is an aurora on Mercury, but it鈥檚 only visible in X-rays coming off the planet.
Will studying space weather on Mercury teach us about similar phenomena on Earth?
The BepiColombo mission consists of two spacecraft; we鈥檒l have one close to the planet and one far away, so that we can get a measurement of the magnetic field close in and then at a greater distance. We鈥檒l see the solar wind, and then a few seconds later it鈥檒l hit the planet. So this will be like getting a view of an extreme example of the solar wind hitting Earth鈥檚 magnetosphere.
The physical process that drives space weather on Earth is called magnetic reconnection, where magnetic field lines store energy and momentum from the solar wind, which is then released and results in the aurora that we see. This process is the same on Mercury, but the rate is crazy. We鈥檙e trying to understand the fundamental physics behind this solar wind-to-magnetosphere coupling. On Earth, the biggest space weather events happen so seldom that I鈥檓 never going to have a chance to measure one 鈥� though if one does happen it could be really catastrophic to our electronic infrastructure. So yes, by studying Mercury I鈥檓 trying to understand what would happen with a big space event on Earth.
Will the instruments you worked on help us solve any of the big mysteries about Mercury?
They might. The spacecraft has two special instruments, one of which we built at the University of Leicester called MIXS, the Mercury Imaging X-ray Spectrometer. One of these instruments points towards the sun, the other points towards the planet. The idea is that the sun gives off X-rays all the time, and when a solar X-ray hits the surface of the planet, it causes the surface layer of atoms to fluoresce. Our instrument picks up those X-rays and they can be used to tell us about the composition of the surface. This might help us unmask the identity of those mystery materials covering the ice at the poles.
Then there鈥檚 this issue about Mercury鈥檚 core. We know that Mercury鈥檚 core is 85 per cent of its radius. That鈥檚 massive; this planet is almost all core! For comparison, Earth鈥檚 core is maybe 30 per cent of its radius. Why Mercury has so much core compared with the other planets is a really big open question, so we hope we鈥檒l get more information. One of the ways we鈥檙e trying to work out what happened to Mercury is by using the ratio of different elements on the surface, like potassium and thorium, because this could help us deduce the collision history of the planet 鈥� in other words, what kinds of things have hit it in the past. That might help us figure out why Mercury looks the way it does.
So do we think Mercury might have been smashed about aeons ago?
There is a that it was originally much larger and some massive collisions early in its life blasted away the outer layers. That would explain the apparently oversized core. But other people suggest that perhaps it looks unusual because it actually formed somewhere else in the solar system and then migrated inwards. It has more metal than it has a right to given its size and location 鈥� but maybe that鈥檚 because this isn鈥檛 its original position. Part of the reason this has come up is because we often see planets around other stars in locations where they cannot have formed 鈥� so we know in principle that planets can move and migrate.
Why Mercury has so much core compared with the other planets is an open question
Coming back down to Earth, tell me about competing in the BBC show ? That must have been a wild ride.
I didn鈥檛 know what to expect. In one of the tests, we had to take our own blood, and I鈥檓 pretty squeamish! Stabbing yourself in the arm is pretty stressful. There was a test to drive a Mars rover, which I massively failed at because I got the rover stuck in a cave. And there was a test where they submerged us in a swimming pool while inside a capsule that we had to escape from. Having a camera on you at all times for six weeks was interesting in its own right. We did over 40 challenges that spanned a huge range of disciplines, from psychology to fitness, teamwork to logical problem solving. We never knew what was coming and there was no feedback. It was a crazy experience!
But you won! How did it feel?
It was amazing. I wasn鈥檛 the best at everything, but I won because I was a fairly steady pair of hands. At the end, I was convinced someone else was going to win. We were standing in a row and they announced my name, and I just absolutely froze. My jaw dropped and they had to film it again. I kept thinking I didn鈥檛 do well in the tasks, so that gave me an interesting insight into my own psychology.
Would you go to space now?
If someone wants to buy me a ticket, I鈥檇 definitely go.
You鈥檝e also been a high-altitude mountaineer for many years. Where have you climbed?
When you start climbing, you tend to start with popular mountains because you don鈥檛 really know what you鈥檙e doing. I started out in the Andes, and then I went to the Himalayas. I realized that I really enjoy complete remoteness, and I really don鈥檛 like being in a situation like Everest, where there鈥檚 a queue of people going up the mountain. So I started climbing more and more in the Andes.
I hear there was an algorithm involved at some stage鈥�
I have access to a supercomputer here at the university. I asked some colleagues for a digital elevation model of the Andes and I wrote some code that would come up with a list of mountains over 5000 metres. There were dozens of unnamed and unclimbed peaks: there are 1042 mountains above 5000 metres in the Andes. So I started going to climb these unclimbed mountains.
How many have you bagged so far?
About 30 above 6000 metres and the same above 5000 metres. These mountains are difficult to get to and hard to climb, but sometimes we鈥檇 get to the summit and we鈥檇 find Incan remnants. The Inca had climbed these mountains and built small structures, little towers a metre high, and no one knows why they built them. We weren鈥檛 the first to climb some of these after all. We鈥檇 get to the top and find the Inca had been there centuries ago, which is really cool.
When did you last climb one of these mountains in the Andes?
A few years ago. Covid put an end to it because there was no travelling. Then I joined mountain rescue as a volunteer, and now I spend a lot of my time living in the Peak District rescuing other people who鈥檝e come to grief in the mountains. I鈥檓 putting those skills to good use.
Tell me more about the rescue side of things. It is worlds apart from studying Mercury.
We get called out up to 200 times a year. Last weekend, we had a girl who fell bouldering and almost ripped her foot off and someone who had a serious head injury in a really remote place. I mentioned I鈥檓 really squeamish, so the one thing I always try to do is think about the areas I need to improve. I wouldn鈥檛 have believed it would be possible for me to deal with injuries like these, but now I鈥檓 much more confident. I love my job and I love studying Mercury, but I don鈥檛 feel like I鈥檓 actively helping anybody. So it鈥檚 a really meaningful thing to spend time doing.
