Journey to the Asteroid Belt

Dave on Earth (11:57 AM): Top of the morning to you, Mark. This is Dave Mosher of Discovery.com

Planetary SciGuy (11:57 AM): Hi Dave

Dave on Earth (11:57AM): Looks like you got logged in ok; thanks for taking the time to chat!

Planetary SciGuy (11:58 AM): No prob - my pleasure.

Dave on Earth (12:00 PM): My first question is this: Who are you?
The follow-up: where are you typing from?

Planetary SciGuy (12:01 PM): I'm Mark Sykes, Director of the Planetary Science Institute, a private non-profit dedicated to solar system exploration. The headquarters are in Tucson Arizona.
So I'm typing from my office in Tucson.
PSI is involved in a number of NASA missions - the rovers on Mars, Mars orbiters, Cassini, Mercury Messenger and the Dawn mission (which I'm a part of).

Dave on Earth ((12:03 PM): Thankfully the hotel had a pool the when I was in Tucson a couple of weeks ago - otherwise I would have cooked.

Planetary SciGuy (12:03 PM): That was our spring weather. It's only getting warm now :)

Dave on Earth (12:04 PM): Mental note: Do not visit AZ in the summer
At any rate, this Dawn mission you mentioned - can you tell me a little bit about it?

Planetary SciGuy (12:05 PM): Dawn launched in September, and the spacecraft is now headed to the Asteroid Belt to rendezvous with the largest asteroid (Vesta) then the smallest planet (Ceres).
Right now there's not too much going on; we're preparing for a Mars gravity assist next February, then it will arrive at Vesta in 2011.
We study Vesta for about 8 months, then continue on to Ceres, arriving in 2015.
It is the first multiple rendezvous mission, which is enabled by ion propulsion.

Dave on Earth (12:05 PM): Lots of stuff to pick your brain about here, but let's start with the who planet thing.
When does a huge asteroid become a planet?

Planetary SciGuy (12:07 PM): Planets are defined from a geophysical perspective as round things that orbit stars. Round - massive enough for gravity to overcome the mechanical strength of the material. When an object is big enough to get round you start seeing geology.
Vesta - our first target - we think formed dry, heated up from radioactive elements decaying inside, and melted. It formed an iron core and its surface is covered with lava (basalt). We see that from its spectra we observe from the earth.
Some time in the past, an enormous object collided with it, making a giant crater covering its south pole.
Debris ejected from Vesta is still hitting the Earth today (and has been for some time) - in fact, we think about 5 percent of all meteorites falling on the earth are from Vesta.

Dave on Earth (12:10 PM): So it's our celestial trouble maker, so to speak.
Now what's the story with Ceres?

Planetary SciGuy (12:11 PM): Ceres - our second target - formed with a lot of water, and Hubble shows that it's smooth and round.
In fact, its surface is covered with clay!
Recent models suggest that Ceres might have an ocean under all that clay. Which then begs the question about whether there could be life there!
By the way, we think that clay is there because Ceres is brighter than other dark asteroids - so clays and other bright materials may be deposited on the surface via liquid water.

Dave on Earth (12:13 PM): Very cool.

Planetary SciGuy (12:14 PM): If Ceres has a subsurface ocean it would be a far nicer target to explore than Europa - Jupiter's giant satellite that also has a subsurface ocean.
Ceres is much closer to the Sun and there's not such a severe radiation environment like there is within Jupiter's magnetic field that Europa orbits within

Dave on Earth (12:14 PM): Obviously Dawn hasn't reached Ceres yet, but knowing what you know about the planet - clay, a potential ocean, etc. - would you go?
And what do you imagine it'd be like to stand on the surface?

Planetary SciGuy (12:15 PM): I AM always game to go...
Standing on the surface of Ceres, I wouldn't expect to see a lot of features like mountains - maybe low rolling hills - because the outer layer is ice rich and cannot bear the weight of a mountain for a long time.
Speaking of which, clay is formed in the presence of liquid water - perhaps beneath the surface. Would there be big white patches of evaporites like we see around geysers on Earth? Perhaps water volcanism?

Dave on Earth (12:18 PM): Water volcanism - like Old Faithful?

Planetary SciGuy (12:19 PM): Maybe a lot of Old Faithfuls!
I also wanted to say that Ceres may have a very thin atmosphere.
We have had no way to confirm it, but I'm thinking a satellite called GALEX might do the trick.
If there is an atmosphere there, we need to be a little concerned about the potential effect of drag on the Dawn spacecraft...

Dave on Earth (12:21 PM): ...and getting stuck in the mud, so to speak.
What other kinds of risks does Dawn face? Seems a little crazy to venture into the Asteroid Belt.

Planetary SciGuy (12:22 PM): Well, as a co-investigator and member of the science team, I'm working on a plan to search for satellites around Vesta.
Just to make sure we do not bump into anything when we arrive there in 2011.
Aside from any possible satellites around Vesta, there is a lot of material out there. Fortunately it tends to be pretty far apart, so the chances of running into another asteroid are pretty slim.
Fyi, I need to head out shortly.

Dave on Earth (12:24 PM): Gotcha. Before you leave, a couple more questions.

Planetary SciGuy (12:24 PM): OK

Dave on Earth (12:25 PM): Did you ever imagine you'd be visiting a strange watery world in the asteroid belt when you were a kid?

Planetary SciGuy (12:26 PM): Since early grade school I wanted to explore space. So, I'm sort of living my fantasy!

Dave on Earth (12:26 PM): Thanks. And my last question:
What's so important about doing all of this, exploring Ceres and Vesta?

Planetary SciGuy (12:28 PM): The more we learn about how planets form and work, the better understanding we have about how our own planet works (we are a long way from knowing everything!).
If we stop learning, we start dying.
Also, exploring the neighborhood is an investment in our own future - especially if that future ever involves expanding off of our planet of origin!

Dave on Earth (12:30 PM): Thanks for chatting, and good luck getting to the Asteroid Belt!

Planetary SciGuy (12:31 PM): Thank you!

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