NASA Spacecraft Explores Frozen World at Edge of Solar System

Jan 1, 2019

NASA’s New Horizons spacecraft, which visited Pluto three years ago, flew by another frozen world in the outer regions of the solar system last night. Ultima Thule is now the most distant object ever visited by a spacecraft. Will Grundy of Flagstaff’s Lowell Observatory is one of the scientists involved. He spoke with KNAU’s Melissa Sevigny from mission control in Maryland.

Artist illustration of flyby
Credit NASA

How it’s going over there?

Everybody’s very excited because the spacecraft just phoned home earlier today. That means the encounter went as planned and the data recorders are full of great scientific data. It’ll take us a long time to get the data but we’re all excited about seeing it.

It’s going to take a year and a half to get all that data down, just from last night’s flyby?  

That’s right, the bit rate is something like 1,000 bits per second. Probably not all that many listeners when we have modems that were that slow. Even in the early AOL days people had 24 kilobit modems, and that was pretty slow. We’re at 1 kilobit. 

Tell me a little bit about this object Ultima Thule, why are we going to look at this object?

We’re going to this object because we can get to it. It was not easy to even find an object we could get to. It happens to be what we call a cold classical Kuiper Belt object, which means it’s really in the outermost zone where solid bodies formed in the solar system, and it’s still where it formed effectively. Not much happens out there, the rate of collisions should be very, very slow. Perhaps the shape still remembers the processes that led to its formation, so we’re very excited to see what the shape is in a little bit more detail than what we saw from today.

OK, so this is like a time capsule from the early solar system.

Yeah, that’s a good way to think of it. The solar system formed small bodies called planetesimals and those went onto to form larger bodies and ultimately planets, even giant planets like Jupiter and Saturn and so on. This is a leftover from that early stage, this never got into a planet. We have much closer examples of this sort of thing in the asteroid belt, but everything is going around much, much, much faster, and they crash into each other more violently. It’s like the inside track on the racetrack, they go around faster there and the collisions are more violent, and so a lot of the original appearance of the bodies has been obliterated, whereas something out in the slow track, in the Kuiper Belt, might still record its original appearance.  

Tell me a bit about your role on the New Horizons team.

So I’m a co-investigator, which means I was one of the people who wrote the proposal to NASA to create the mission in the first place, and I lead the surface composition science theme team. My team is eagerly awaiting data which comes down tonight and tomorrow night which should tell us some hints about the composition of the object. I can’t say anything about that yet because we really know nothing yet….. But we’re excited to get down to work and have some science to dig into. This is a completely different object than Pluto, in the sense that Pluto is a very active world today, and a lot of the science was trying to understand that activity, what kinds of processes were shaping its surface. This is a body that probably hasn’t changed much in a long, long time, and so we’re trying to read history in its surface and get back to the conditions when it formed.

And we’re a billion miles further than Pluto now?

Yeah, Pluto was about three billion miles from the sun, and Ultima Thule at the time of the encounter is about four billion miles from the sun. A billion miles every three years, that’s a pretty good rate of speed.

That’s not bad. Will Grundy, congratulations and good luck with the mission.

Thanks Melissa.