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Hello to our early arriving chat participants! Today's Space Scientists Online/NASA On the Cutting Edge chat with Beth Ellen Clark will begin at 10:00 a.m., Pacific Standard Time.

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Hello and welcome to today's Space Scientists Online/NASA On the Cutting Edge chat with Beth Ellen Clark from Cornell University. Small asteroids continually impact the Earth. Some believe a large one may have caused the extinction of the dinosaurs. Beth is one of many scientists who continue to study the effects small asteroids have had on Earth.

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And now, here is Beth Ellen Clark to answer your questions.

[ beth - 14 - 10:03:11 ]
RE: [Lydia] If an asteroid hit the earth, how big would it have to be to be destructive?
Lydia, estimates I remember are that if an asteroid is larger than a meter in diameter it will not burn up completely in the atmosphere, and hence could impact Earth with enough force to cause some local damage. If it is larger than 1000 meters, it will cause VERY significant damage.

[ beth - 19 - 10:08:52 ]
RE: [Micah-Mrs.McLellan/WordsofLife] Where do asteroids come from and why would they hit the earth?
Micah, most asteroids come from the Main Asteroid Belt, a zone of small bodies which orbit the Sun between the orbits of Mars and Jupiter. We believe that asteroids, or fragments of asteroids, are sent on a collision course with other planets as a result of collisions between asteroids. So, if an asteroid in the Main Belt were to collide with another asteroid in the Main Belt with enough force, it could result in fragments which have orbits of their own and which could evolve onto planet-crossing paths.

[ beth - 21 - 10:14:57 ]
RE: [Jacob-Mrs.McLellan/WordsofLife] What are asteroids made of?
Jacob, that's a very good question, and one of my favorite questions to answer because that is what I specialize in: asteroid composition. We believe that most asteroids are made of very old rocks, rocks which were formed from condensation from the swirling cloud of gas and dust which existed during the time our sun was forming, 4.6 billion years ago. We believe we have samples of these asteroids, in the form of meteorites. Meteorites are very different from any of the rocks we find on Earth, but we know they are from outer space (mostly from asteroids) because we can watch them fall to Earth. Many meteorites are composed of strange round blobs called CHONDRITES which must have formed in very low gravity environments - they are perfectly round! Meteorites also contain bits and pieces of minerals which must have existed in interstellar space even BEFORE our sun formed 4.6 billion years ago. They are very interesting rocks.

[ beth - 24 - 10:20:25 ]
RE: [Ariel-Mrs.McLellan/WordsofLife] Why would it be important for NASA to visit an asteroid?
Ariel, it is important for NASA to visit an asteroid, I believe, because we don't understand their structure (how the minerals are put together in the asteroid's interior) and because we don't understand very much about their history or the processes which affect them. By sending a NASA spacecraft to visit an asteroid we can study their shapes, densities (are they solid like rocks or could they be full of air spaces), surface craters (how many craters are there and how big are they?), and we can also study how asteroid surfaces are being affected by the space environment. Also, although we know that asteroids are probably composed of rocks like meteorites, we do not know exactly which meteorites come from which asteroids, and spacecraft data can help us to answer these questions.

[ beth - 25 - 10:23:01 ]
RE: [Micah-Mrs.McLellan/WordsofLife] Is there a NASA mission planned to land on an asteroid?
Micah, yes, another good question! There is a NASA mission in the planning which will land a rover on the surface of an asteroid. It is in collaboration with the Japanese Space Agency and the mission is called MUSES-C. I am hoping to be one of the scientists chosen to work on that mission, so your question is particularly timely! If we can land a rover on an asteroid, it will be neat to drive it over the surface and peer into craters...!

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[ beth - 30 - 10:28:48 ]
RE: [Ariel-Mrs.McLellan/WordsofLife] How do we know if a meteorite came from an asteroid or a comet?
Ariel, actually, that question has kept scientists pondering for a long time. One way to tell if a meteorite came from a comet would be to search for evidence of volatile compounds, such as ices of water and ammonia. If it happens that we don't find any volatiles, we can't be absolutely certain that the meteorite is NOT from a comet, unfortunately, because the volatiles could have all melted either during passage through the Earth's atmosphere, or out in space in direct sunlight. There are very small particles caught in the Earth's atmosphere by high-flying jets which are believed to come from comets, and they have slightly different compositions than small meteorite particles, but for the most part it is very difficult to be sure that a meteorite is definitely from a comet.

[ beth - 32 - 10:32:18 ]
RE: [Brad-Wubbena/BowenIntermediate] My 5th grade class is doing research for the purpose of building a self-sufficient space station to be placed on another planet or moon. One of the problems they have encountered has to do with air. Since it is a self sufficient unit, other than plants, is there a way of producing the air they will need?
Brad, people need air that has a similar mix of gases as we breath on Earth: oxygen, nitrogen, water, and carbon-dioxide. There are ways to synthesize these gases from more elementary gas atoms, and many of these gases are the products of chemical reactions. So the answer is yes, there are ways to MAKE air on another planet.

[ beth - 35 - 10:35:51 ]
RE: [Ariel-Mrs.McLellan/WordsofLife] Are asteroids ever a good thing or do they always destroy?
Ariel, yes, asteroids are definitely a GOOD thing. For one thing, I think they are very interesting rocks to study - they tell us A LOT about the early SOLAR SYSTEM, in fact they are our most IMPORTANT source of information about what our solar system must have been like 4.6-4.5 billion years ago. Asteroids do not always destroy - in fact I would say that most of them do not! Most asteroids quietly orbit the sun or harmlessly collide with one another, very few of them ever collide with other planets!

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Some of you may be interested in checking out the archives of some of our live events focusing on the International Space Station. You can find out more at http://quest.arc.nasa.gov/ltc/sto/iss. Check it out!

[ beth - 38 - 10:38:11 ]
RE: [Lydia-Mrs.McLellan/WordsofLife] Are asteroids a threat to the International Space Station?
Lydia, I believe that the engineers of the International Space Station have allowed for asteroid/meteorite impacts of a certain force in their construction of the station. Of course, if a very rare LARGE asteroid were to collide with the station then there could be trouble, but most asteroids are small, and will not exceed the danger limits to the space station.

[ beth - 39 - 10:41:31 ]
RE: [Micah-Mrs.McLellan/WordsofLife] What kind of a rover would you use to land on an asteroid?
Micah, to land a rover on an asteroid, you would have to use consider the fact that the gravitational pull on as asteroid will be very small. A rover will need to be able to bounce on the surface because any small nudge will send it into the "air" very easily.

[ beth - 40 - 10:44:25 ]
RE: [Micah-Mrs.McLellan/WordsofLife] The earth has an atmosphere to help protect it from asteroids. Will the International Space Station have anything to protect it from asteroids, meterors or comets?
Micah, I think that the International Space Station is carefully planned to withstand small asteroidal/meteoritic impacts. It must be! Large impacts will cause trouble, but most impacts will be within the tolerance of the construction plans.

[ beth - 42 - 10:48:32 ]
RE: [Micah-Mrs.McLellan/WordsofLife] Do you think the STARDUST mission will answer the question of the differance between an asteroid or a comet meteorite?
Micah, I don't know very much about the STARDUST mission science goals, actually. I will have to look up the answer to your question. The ability to tell the difference between asteroidal and cometary dust particles will require very precise measurements and the instrumentation for those measurements. I will try to learn the answer to your question, its a good one!

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We have about 10 minutes left for Beth to answer your questions. For those of you leaving us, please share your thoughts about today's chat with us at http://quest.arc.nasa.gov/qchats/qchat-surveys.

[ beth - 45 - 10:50:40 ]
RE: [Richard-Stephanie/Edmonton] Can a human being land on an asteroid?
Richard, a human being has never landed on an asteroid, but in theory there is no reason why one could not do so! The trouble is that it would be very easy to jump off an asteroid into outer space!! Every time you took a step you would have to be very careful not to launch yourself.

[ beth - 47 - 10:56:15 ]
RE: [Stephanie/Edmonton] Was anything learned from the close encounter of Eros by NEAR?
Stephanie, yes, we have learned a great deal about Eros from the close encounter of NEAR, in December of 1998. Some of the MOST IMPORTANT things we learned about were the shape, size, mass and density of Eros. With this information we can plan a very detailed maneuver to get the NEAR spacecraft into orbit around the asteroid, and we can also plan a very detailed method of mapping the surface of the asteroid to achieve the science goals of the mission. Just think - if the close encounter had revealed that Eros was shaped like a pencil, we would have had a very different orbital plan than if we had found it to be shaped like a sphere. In reality, we found that its shape was somewhere in between those two extremes - it is more like a peanut.

[ beth - 48 - 10:59:39 ]
RE: [Jacob-Mrs.McLellan/WordsofLife] We read the book "The Little Prince". The prince lived on an asteroid with his flower. We know this is fiction, but could there be life on an asteroid?
Jacob, most scientists do not believe that life could currently exist on an asteroid. Life has arisen on Earth due to the existence of very many complex interacting reasons. On an asteroid, things are very simple - there is no atmosphere, no running water, etc. An interesting thing to note, however, is that we actually find hydrocarbons in meteorites and hydrocarbons are some of the precursor materials for the synthesis of living cells. It is interesting that these materials existed as far back as 4.5 billion years ago, the age of meteorites!

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We will now be ending our chat Beth Ellen Clark from Cornell University. We would like to thank everyone for joining us today. Our very special thanks to Beth for her thoughtful responses to our questions, and for sharing her career experience and expertise with us.

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As a final reminder, we ask for your feedback on today's chat, which you may give to us at http://quest.arc.nasa.gov/qchats/qchat-surveys.

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We hope you can join us for our next Space Scientists Online chat on April 8 with Daniel Berdichevsky from NASA Goddard Space Flight Center. Be sure to read Daniel's autobiography at http://quest.arc.nasa.gov/sso/team/berdichevsky.html in order to prepare for this chat. Check the Space Scientists Online chat schedule page at http://quest.arc.nasa.gov/sso/chats/sched.html to learn more about these upcoming events. Also check our schedule of events page at http://quest.arc.nasa.gov/common/events to learn about other upcoming chats with NASA experts.

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RE: [Allofus-Mrs.McLellan/WordsofLife] This chat about asteroids had a deep impact on us - Thank you and good bye!
We're glad to have you online today, Mrs. McLellan's class. Have a good day!