Pictures of Pluto

DW: In 2006, Pluto was reclassified as a dwarf planet. What do we know about it?

Professor Andrew Coates: Yes, it's a dwarf planet, and this is a new class of object which was defined in 2006. So, Pluto - when we were all growing up - used to be a planet. But it was demoted in 2006 to be an ice dwarf, and that's in response to discoveries about the outer part of the solar system, where there appear to be several objects, possibly many objects, which are approaching Pluto in size. It will be the first one of this new class of objects which will be explored by a spacecraft.

So, the other objects in the solar system include, of course, the planet we're on, Earth, which is one of the terrestrial planets, a rocky planet towards the inner part of the solar system. Then there's the gas giants. Those are [made of] hydrogen and helium - stuff from the solar nebula, caught by the large planets: Jupiter, Saturn, Uranus and Neptune. And then Pluto is in this new class of planets, the ice dwarf planets.

So it's not only that we will learn about Pluto, but about a new category?

Yes, we'll learn about a new category. There should be quite a lot. The International Astronomical Union at the moment recognizes five of those, of which four are in the vicinity of Pluto and beyond. But also interestingly, Ceres, which is one of the asteroids - this is one of these [newly categorized] objects as well - is being visited by another spacecraft this year, which is the Dawn spacecraft. And that will be getting to Ceres in March.

When the New Horizons spacecraft starts taking photos or images of Pluto, it will still be about 130 million miles away (209,000,000 km). What can we expect to see? Will we start to get very clear images?

The best images we have at the moment of Pluto [look like] a disc with light and dark segments to it, and they're really not very well resolved at all. These are from the Hubble Space Telescope. So in mid May - that's when the images from the Pluto mission will start to get better than Hubble. We'll start to be able to see the surface of Pluto and its features for the first time. Who knows what will be revealed? And we'll also be looking at the moons of Pluto - Charon and several other moons which we know of, and probably more moons will be found, possibly rings. And it will be possible to study something which we do know about Pluto, which is that there is a weak atmosphere. Because Pluto spends some of its time inside of the orbit of Neptune and some of it outside the orbit of Neptune, when it gets far, far away, the atmosphere collapses, we think. So getting New Horizons there to see that is going to be very important. It's a tenuous atmosphere - but mainly, nitrogen and methane - so it's possibly like the Earth's early atmosphere.

This is predominantly an American mission. But as a British or European scientist, what do you hope to get from this? Are you going to be able to get your hands on the data?

We do have very good collaborators on the team and good relationships with them, and of course the data will be published and available to everybody to look at and compare with other data. Space science is a huge international endeavor, but this particular mission uses all American instruments. Itt's a US spacecraft. There is no European cooperation in the major parts of the instrument team. And that is unlike Dawn - that has a lot of German and Italian scientists involved in the teams, and the camera itself comes from Germany. But that's not the case with Pluto, and I think that was done for cost and political reasons.

But it's still of value to all people?

Oh, absolutely, yes. They're doing exploration which is looking at the boundaries of knowledge, and this is being done for the benefit of all mankind, including European scientists! In our particular case, we're interested in how solar wind interacts with Pluto. This is something which we've studied with comets and planets in the solar system and other objects for many years. And so putting Pluto into context is going to be very exciting, because the radius of gyration of a charged particle of Pluto is very, very large, and that creates a really kinetic interaction where the particles are very important. There are some commonalities with comets, and so from our work on the Giotto mission and the Rosetta mission, that's going to be very relevant to what we're going to be able to look at with Pluto.

Professor Andrew Coates is the head of Planetary Science at the Mullard Space Science Laboratory, University College London. He is also the principle investigator of the PanCam instrument on the ExoMars 2018 rover mission. The PanCam team is an international collaboration, including the German Aerospace Center (DLR), which aims to provide wide-angle stereo and high resolution images on the Martian surface and a context for subsurface drilling to look for signs of life on Mars.