NEAR February 17, 2000 Press Conference Quotes

Selected Comments
Press Conference on Early NEAR Science Returns
February 17, 2000
NASA Headquarters, Washington DC

Dr. Thomas Morgan
NASA Headquarters
NEAR Program Scientist

I want to welcome you here to first of what I expect will be many briefings on the results of the NEAR mission. I think you'll be excited by the results of this briefing, and I totally expect there will be many more exciting results over the next year . . .

I would like to briefly add that this is one of a half-dozen missions to minor planets, four with NASA and two with overseas partners, that we expect to see launched - or in one case has been launched - in the next few years. So over the next decade I expect we'll see a change in our understanding of these extremely important objects . . .

Dr. Andrew Cheng
JHU Applied Physics Laboratory
NEAR Mission Scientist

Christmas came a couple of days ago and it's not over yet. We have a couple of rooms full of scientists still happily tearing open their presents, and this will go on for a year . . .

[The images provide] tantalizing hints that the asteroid has a layered structure that seems to extend globally throughout the body of the asteroid - as if the asteroid might have layers. The implications of this - and we have a lot more work to do - are that this kind of layering would most likely come about if Eros was once part of a much larger body. So, this could be an indication that Eros is the type of asteroid that was part of a planet . . .

Other things we've seen on the asteroid are things that have literally never been seen on asteroid before, such as a really strange bright spot. We also see grooves and boulders and lots of wonderful things . . .

Dr. Mark Robinson
Northwestern University
NEAR Imaging Team Member

In early January, we got our first glimpse of Eros. We started taking rotation sequences, or a picture of the asteroid every 26 seconds, which is equivalent to half-a-degree rotation. We do this 780 times and we capture more than one rotation of the asteroid, and from those frames we can build a rotation movie . . .

Eros is fairly irregular and heavily cratered, indicating its surface is not young. There's a crater in the backside, or concave side, of the banana shape, and it's about 5.5 kilometers or roughly 3 miles on diameter . . .

We're very excited. Even in these images we can see that Eros is not a boring object, that it's not just a rock floating out in space. There's a lot of neat geology going on . . .

In the images you can see several large boulders. We're excited about this because these boulders come up from depths in the asteroid, so they give us a look at the inside of the asteroid. We're going to be seeing the asteroid at more than 10 times the resolution we see here . . .

When the images came in and when they were pieced together, I was stunned speechless by the beauty of this asteroidal landscape. After that feeling wore off, it was like. 'Oh my gosh, we're actually in orbit around this irregularly shaped body.' We kind of take some of these things for granted, and this is an incredible feat by both the navigation team and the mission operations team to actually put us into orbit and keep us in orbit . . .

There are grooves and ridges, and mansion sized boulders, and you can see a bright patch that has an albedo, or a brightness, which is about 25 percent brighter than the rest of the asteroid, and that's a very large difference from the materials you expect on the surface. We're going to be keeping our eyes on that when we get to the higher-resolution data. This is potentially something of a different composition relative to the average composition of the asteroid, so that's a neat feature to keep our eyes on . . .

You can also see the ridges and grooves going up and down a gully, and on the back side, some other sort of ridge system. We don't really know what it means yet, but it's an unambiguous indication there's some sort of global structure in the asteroid, which tells us how the asteroid was put together . . .

Over the next several months we'll be seeing this in much higher resolution. We've seen some neat stuff, but I can't imagine what we'll see over the next year . . .

Dr. Donald Yeomans
Jet Propulsion Laboratory (JPL)
NEAR Radio Science Team Leader

The magnificent images of Eros we get are made possible by a successful orbit insertion burn. The spacecraft was sneaking up on the asteroid at 10 meters per second, or about 22 miles per hour. We put on the brakes and went into an orbit of some 200 by 280 miles, but this is not business as usual. The communications satellites around Earth are going something like 6,700 miles per hour; in orbit around Eros, were going 2 miles per hour. That's a slow walk . . .

For a celestial object, Eros is has an extremely low mass. If I were standing on surface of Earth and weighed 200 pounds, and transferred myself to Eros, I'd weigh a svelte 2 ounces. If I could jump 3 feet on Earth, I could jump about a mile on Eros and run the risk of putting myself in orbit . . .

It's a big challenge for the navigation team at JPL and the operations team at APL to keep the spacecraft in orbit. The small mass itself isn't really the problem. If [Eros] were a spherical object, we could put the spacecraft in orbit and it would stay there pretty much without having to mind it. But it's harder to put an object in a direct orbit around an irregularly shaped object. If you don't watch it carefully, it can evolve into an orbit that smacks into the surface or wanders off into interplanetary space . . .

So it's very tricky. We have to monitor it continuously and make adjustments from time to time to bring it back to where we want it to be . . .

The mass determination is important for navigation purposes because that determines the size of the orbits that will result at a particular stance, but its also important from a scientific point of view . . .

So the mass, combined with the volume which we will get later on in the mission, will give us the bulk density. One of the important results we got recently is that the bulk density of this object is about 2.4 grams per cubic centimeter. Water is 1 gram per cubic centimeter - 2.4 is just about the density of the Earth's crust - so it seems likely that were dealing with a far more solid object that the Mathilde asteroid, which was 1.3. If we had a dish large enough and it was bit lighter, Mathilde would float . . .

So this is a much more solid object, but the jury is still out on what kind of porosity were talking about here . . .

Dr. James Bell
Cornell University
NEAR Imaging Team Member

What an exhilarating and exhausting week it's been . . .

The Near-Infrared Spectrometer is operating beautifully. It has returned more than 10,000 measurements of the surface or Eros since we started making observations during our approach, including some of the first infrared spectral maps of the surface of an asteroid. Some of us have felt like kids in a candy store, expect we get to stay in the candy store all year . . .

We've seen there is very little color on the asteroid from place to place. This relative lack of color at various wavelengths is precisely why we put an infrared spectrometer on the spacecraft in the first place, because to an infrared spectrometer, many rocks and minerals that appear bland to our eyes look very colorful . . .

The instrument works by measuring sunlight reflected off the surface of Eros, and splitting that light up into its constituent colors, just like a prism makes a rainbow. Certain types of minerals absorb some of these infrared colors and provide us with a way to infer the mineralogy of the asteroid's surface . . .

We find minerals like this on Earth, the moon and Mars, so we aren't surprised to see them on Eros. It's wonderful to see them so early in the data set and see the signatures in the infrared coming in so clearly and that the instrument is working so well . . .

We've only had the data on the ground for 72 hours, and we're already seeing wonderful evidence of the compositional and mineralogical change on the surface. We think this data will allow us to make a stronger connection between asteroids and meteorites, and the origin and evolution of Eros itself . . .