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Phoenix Finds A Salt Compound On Mars

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Phoenix Finds A Salt Compound On Mars

Space

Phoenix Finds A Salt Compound On Mars

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IRA FLATOW, host:

This is Talk of the Nation: Science Friday. I'm Ira Flatow. A little bit later in the hour, drug testing in the Olympics, and the latest astronomy news from the solar system and beyond. But staying closer into our solar system, news from Phoenix, that's NASA's latest visitor to Mars. And since its arrival in late May, the Lander has been digging up icy Martian soil, depositing samples in its onboard labs for analysis. And last week, mission scientists announced Phoenix's biggest finding to date, proof positive of water in one of the samples in the form of ice.

And this week, scientists held a surprise news conference, hoping to bat down unconfirmed, unjustified rumors about possibly the discovery of life on Mars and also offering new findings of a toxic mineral in the soil samples. The mission's chief scientist joins us now to clear things up. Peter Smith is the principal investigator and senior research scientist at the Lunar and Planetary Lab at the University of Arizona in Tucson. Welcome back to Science Friday.

Mr. PETER SMITH (Senior Research Scientist, University of Arizona; Principal Investigator, Phoenix Mars Mission): Thank you, Ira. Nice to talk to you again.

FLATOW: Thank you. Busy week for you.

Mr. SMITH: This is fabulous. This is the best time of our project. We're really in the midst of getting our science results right now.

FLATOW: And tell us about how you're so sure that you've actually touched - tasted water this time.

Mr. SMITH: Well, we managed to scoop up some of the very hardest material on the surface that had been frustrating us for some time, because it tends to stick to our scoop when we try and put it in our instrument. And this time, we managed to get some of that very hard material, and guess what. It melts at the melting point of water, and it has the signature in our mass spectrometer, a massive peak - I'm sorry - a signature at peak 18, in other words, oxygen and two hydrogens. So, I think we've really nailed it now that it has to be water.

FLATOW: And you would believe that everything around it is the same water?

Mr. SMITH: Well, that's our first assumption, yes. But there are some interesting other features around that could be other materials, so we're still in the midst of our investigation.

FLATOW: The robotic arms scooped this up. Did it have to go very far below the surface to find it?

Mr. SMITH: Amazingly, it's only two inches below the surface. This is a permafrost region on Mars, and we suspect that the entire plains in front of us is covered in about two inches of soil, and then it's really just almost like a frozen ocean.

FLATOW: And so, what's next? Do you try to get more samples?

Mr. SMITH: Yes, that's what we're doing right now. We're trying to get as many samples as we can from the range of materials available in front of us, and what's available is the peaks of our little polygon features and the troughs in between them. We've now sampled the peaks, and we're looking under the troughs.

FLATOW: If the major objective of your mission was to discover water, do you declare victory and go home now?

Mr. SMITH: Well, actually, the - it's true, it was to discover water. But we're here to discover liquid water, and what we've found now is water ice. So, the question that is posed for us is, does that ice ever melt? And we have a couple ways to try and determine that. Mostly, we're looking at the minerals and chemicals in the soil in association to the ice to see if they have been affected by liquid water.

FLATOW: Mm-hm. And you found that interesting mineral that has raised a bit of a controversy. Tell us about that.

Mr. SMITH: Yeah. I mean, this sent us - sent me, anyway, back to the textbooks to try and figure out what a perchlorate is, and our chemistry experiment determined there's a fair amount of perchlorate in the soil. And so, what we've learned about it, it's a very stable chemical. It's used actually for rocket fuel and stable at room temperature, I should say, because if you heat it up hot enough, it really...

FLATOW: Kaboom.

Mr. SMITH: Ignites. Yes. But in a rocket, you see, when you leave the atmosphere, there's no oxygen to work with the fuel. I mean, if you put a match to lighter fluid, you have to have oxygen in association, and usually it's in the atmosphere. But this material provides oxygen to the fuels. And so, when you heat it up, it'll break into an oxygen-rich environment. But at room temperature colder where we are in Mars, it's extremely stable, and it's also very soluble in water. And so, we can use it to trace where liquid water has carried it in the Martian surface.

FLATOW: So, you don't think it's - being part of a rocket-fuel system, you don't think it's a contaminant you brought with you?

Mr. SMITH: We have been researching this very thoroughly, because it's an obvious first question, and we cannot find a source for this much perchlorate under the surface. We actually burned the perchlorate, so there shouldn't be any left when we get there. And there's just a tiny amounts, just grams of perchlorate, that's brought with us. It couldn't be spread evenly over the surface to see the signatures we see.

FLATOW: Does the fact that it is a perchlorate and usually toxic to life forms on Earth, would that mean it could be toxic to any life forms you might want to discover?

Mr. SMITH: Well, toxic is an interesting word. My father used to say the difference between and poison and medicine is the dosage, and they actually, some years ago, used to use perchlorate as a medicine for hyperthyroidism.

FLATOW: And so, you don't think that that's the problem here on Mars?

Mr. SMITH: I don't see it - I don't see toxicity as being a big problem. I really don't. It's - I mean, you have to be careful with it, of course. But I don't think it's going to be a problem for most - for future astronauts.

FLATOW: Tell us why you were so surprised to find it. You know, I know that you test out Martian vehicles as close to the conditions on Earth as you can, either in Antarctica, Greenland, places like that, very cold places where things would stay frozen. Do we not find perchlorate there also?

Mr. SMITH: We tend to find perchlorate most commonly in hyper-arid environments, and the kind of the classic place is the Atacama Desert in Chile, where it rains a few millimeters every 10 years, and so the perchlorates are formed in the atmosphere. The UV takes the chlorine that comes off the ocean. As you know, we have a salty ocean and little bits of sodium chloride go up into the atmosphere. They react with the ultraviolet from the sun, and then they're allowed to bound with hydro - I'm sorry - with oxygen, and they form a perchlorate and rains down on the surface, and it's only kept in place when you have a very dry environment. Otherwise, it goes into a solution where the water immediately goes into the groundwater and comes back to the ocean.

FLATOW: I see.

Mr. SMITH: Hyper-arid environments, and of course, Mars is - it fits that well, very, very well.

FLATOW: And how can you tell? You said you could use this to figure out the history of liquid water. How would you do that?

Mr. SMITH: Yes. If the ice were to melt, even every million years or so, the things don't change rapidly on Mars. So, if the ice were to melt and wet the soil over time, you would change the basaltic soils that we expect to find into clays, perhaps, carbonates, sulfates. These are all minerals that are formed through the action of liquid water. And so, we're looking for those what are called altered minerals, altered from their primary volcanic state into other minerals that we commonly see on the Earth. And our instruments are very sensitive to those types of products. We also look for salts. Obviously, if you have something wet, it can leave salts out of the soils, and when it evaporates, it leaves the salts behind. So, a salt-rich clay, carbonated-sulfate environment would say, gee, that was probably wet at one point.

FLATOW: There were some wacky rumors going around this week, whether or not the fact that you had discovered life and kept it secret and told the White House about it and no one else.

Mr. SMITH: Yes. Somehow, the story went out that we've been talking to the White House about some big discovery, but that was news to me, I'll tell you.

(Soundbite of laughter)

Mr. SMITH: I haven't talked to the White House about anything.

FLATOW: Also, did you not get an extension of your mission?

Mr. SMITH: Yes, we did. We have now been extended to the end of September, and this is good news because we haven't had time yet to use all the cells we've brought with us. We're very close to a mission success, which would have been three of our ovens and three of our wet chemistry cells. But we still have others we haven't used, and so it's really important to us to, you know, make as much scientific progress as possible in the short amount of time we have.

FLATOW: Once those resources, those cells, get used and used up, does that mean basically you're done?

Mr. SMITH: Well, we're done as a soil-analysis station and we become a weather station. And then we really are interested in polar climate, you know. It's - you can't study the surface in isolation. It really works as a system with the atmosphere. So, we're studying the water vapor in the atmosphere, how it diffuses to the soils to form the ice layer, and we'd really like to see how the season progresses.

FLATOW: So, I'm thinking of the Mars Rovers that have been going on for years, you know, designed for a few months...

Mr. SMITH: Yeah, but they're not inside the Arctic Circle. When the sun sets, it's 24-hour darkness, and that's going to be a problem for our lander. We do not suspect it will survive.

FLATOW: Considering the failures of the old Polar Explorer Enterprise, you must be - feel very vindicated now, I would imagine.

Mr. SMITH: Oh, I'm just overjoyed. Our project has been blessed, and we feel like we're really making some big strides forward in Martian science, and we certainly haven't completed that process. I'd say we're about halfway through, you know, really getting all the depth of science that we intend to get, and doing the analysis we need to do to understand what we've got, and my gosh, these are complicated instruments. So, you know, we're really at the harvest period right now for our project.

FLATOW: You'll be shoveling more soil into those ovens?

Mr. SMITH: We will and we're doing it today actually. So, stay with us and hopefully we'll have some more really interesting results to present to you.

FLATOW: Well, we're excited to - how much do you already pick up? Is it a spoonful or - give us an idea of how much goes in there.

Mr. SMITH: Yeah, you know, it's not very much. We pick up, oh, maybe a handful, but the amount that actually goes into our instruments is at the level of a few grams for our wet chemistry and even micrograms for our ovens.

FLATOW: Let me see if I can get a quick phone call in before we have to go. Chris in Tucson. Hi, Chris.

CHRIS (Caller): Hey, how're you doing?

FLATOW: Quickly.

CHRIS: I wanted to see, does this change the priority - this discovery change the priority or importance of sending perhaps a less robust probe to Mars to collect the sample and bring it back?

FLATOW: Hm, good question.

Mr. SMITH: I'm not sure what you mean by less robust.

FLATOW: Well, just to bring up - there used to be that Mars Return Sample Mission, I think, that was canceled.

Mr. SMITH: Yes, I think we're very interested to get samples back to Earth, and all of us would love to see that because our laboratories can do such a better job than, you know, doing it from 200 million miles away remotely. We would love to have that happen, but as I understand it, the NASA plans don't show this until later in the next decade. So, I think we're kind of stuck with that at the moment.

FLATOW: I see, you'll just have to keep doing it the old-fashioned way.

Mr. SMITH: The old-fashioned way works very well, frankly.

(Soundbite of laughter)

FLATOW: Well, Pete, we're very happy to talk to you, and we will be checking back in periodically, if you don't mind.

Mr. SMITH: Not at all. We're really on the search for a habitable zone on Mars. We've found one of the three underpinnings of a habitable zone already and that's an energy source, perchlorate. Actually on the Earth, microbes live off of it. They get energy from it, so...

FLATOW: Well, we'll be back.

Mr. SMITH: We're making progress. Thank you, Ira.

FLATOW: Thank you, Peter Smith, principal investigator of the Phoenix Mars Mission, senior research scientist at the Lunar Planetary Laboratory, University of Arizona in Tucson. Stay with us. We'll be right back after this short break. I'm Ira Flatow. This is Talk of the Nation: Science Friday from NPR News.

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