Water on the Moon
Interview with USGS scientist Dr. Roger Clark about his Sept. 24 Science article that suggests water exists on the moon. Imaging spectroscopy led Clark and others to this discovery which opens the possibilities into further moon exploration.
Heidi Koontz: Welcome and thanks for tuning in to this episode of CoreCasts. I'm Heidi Koontz and I'm here today with Roger Clark. Roger, thanks for taking the time to chat with me about your latest science article.
Roger Clark: OK, thank you.
Heidi Koontz: "Water on the moon," isn't this impossible?
Roger Clark: Well, it's a complex, long story and I'll try and make it brief. But from the formation of the moon, it's thought that a Mars-sized body collided with the Earth and broke a part of the Earth and that material then collected into the moon. During that process, everything was molten and it was thought that all the volatile compounds like water were lost.
Some people don't necessarily agree with that, but most planetary and lunar scientists have believed this for a long time. And the Apollo samples have supported that theory that they don't have much water, but there actually was some water in them. But when the Apollo samples were returned to the Earth in vacuum-sealed boxes, but every one of the fields failed so that when the space capsules came down, Earth atmosphere leaked in along with Earth water. And it was thought for many years that all the water people were seeing was actually due to Earth contamination, and it was very, very difficult to prove otherwise.
About a year ago, a group out of Brown University published a paper where they broke open little glass grains and actually found water inside them and proved for the first time very tiny amounts of water.
Heidi Koontz: And you said that the Cassini last passed by the moon in 1999? That was 10 years ago. Haven't things changed up there?
Roger Clark: Well, the Cassini spacecraft when it flew by the Earth was turned on for a very short time - the instruments. And we took some data and then we were turned back off. So, we collected that data, but we didn't have the calibration in order to understand what the data meant. Well, we turned it on briefly at Jupiter but also didn't get to collect calibration data. We didn't get calibration data until we got to Saturn in 2004.
For detecting tiny amounts of water, water is on the spacecraft. And it's very, very difficult to calibrate an instrument in space because there's still residual water on the instrument. So, we need to look at standards where we don't think there's any water like stars. And it took quite a while to gather the star data.And it wasn't until summer of last year, 2008, that this was figured out what the better calibration is that would allow us to make this discovery. And the first papers with this new calibration were just submitted at the beginning of this year. And so, this is the moon one and there's another one. So, the papers started to flow out from this calibration.
Heidi Koontz: OK, interesting. So, your field of science, spectroscopy, is pretty amazing. Can you give a little insight into how this tool helps better understand this water on the surface of the moon?
Roger Clark: Well, spectroscopy is a method for breaking up light into different wavelengths, much like a rainbow does. Or if you have a prism in a science class, you can use the prism to break up the light; only, that's just visible light. There's also infrared, ultraviolet and other wavelengths. And we use infrared wavelengths further out than longer wavelengths than you could see. So, about five times longer wavelengths, four to five times longer than red light. And it's at those wavelengths where the water molecule has an absorption where it absorbs light of that wavelength and it's that specific set of wavelengths that enables us to see the water, specific compounds. This is just one example; we'll do lots more.
Heidi Koontz: Well, it seems like spectroscopy is a great application for many different scientific endeavors.
Roger Clark: Well, yes. It's a combination of both spectroscopy to understand things and imaging. So, that's the field of imaging spectroscopy, which is a relatively new field mainly because technology has only gotten to this point to allow us to do this over the last, say, 20 years. So, there are now imaging spectrometers flying around the Earth in aircrafts and satellites. There is an imaging spectrometer around Mars called "CRISM" and then the Cassini Visual and Infrared Mapping Spectrometer that's flying around Saturn at the moment.
Heidi Koontz: OK. So, what do you think this means for the future of moon exploration?
Roger Clark: Well, with the discovery of spread water on the surface of the moon in direct sunlight is a pretty amazing discovery because that is in particularly the place where it was thought if there was any water, the sun and solar wind and cosmic rays would bake out all of the water so it should be dry, but this shows that it is not.
So, our next step is trying to understand why it's there in the first place. And we have a lot of data from the M3 Moon Mineralogy Chandrayaan-1 Mission. And we'll be analyzing that data to try and understand as much as we can from that data set which should be a lot. And then, hopefully we'll get a new instrument that can do an even more detailed job to tell us more of the story.
Heidi Koontz: So, those are your next steps?
Roger Clark: Yes.
Heidi Koontz: Well, Roger, thank you for taking the time today and good luck with your future endeavors.
Roger Clark: OK, thank you.