This article is from the In-Depth Report Robotic Exploration of the Solar System
Science Talk

A Mars Rovers Once-Over

We look at the state of the rovers currently on Mars, the big accidental discovery by the Spirit rover, and the next-generation device slated to join them in 2010, the Mars Science Laboratory Rover. Interviews with Cornell's Melissa Rice, the payload downlink lead for the rover cameras, and the Jet Propulsion Lab's Michelle Viotti, about the Mars Science Laboratory Rover. Also press conference clips featuring Cornell's Steve Squyres, principal investigator for the science instruments on the Mars Exploration Rover Mission, and Harvard's Andrew Knoll, a biologist with the Mars missions. Plus, we'll test your knowledge of some recent science in the news. Web sites mentioned on this episode include

Steve: Welcome to Science Talk, the weekly podcast of Scientific American for the seven days starting March 5th, 2008. I'm Steve Mirsky. This week on the podcast we're going to Mars, virtually. We will take a look at the current and future rovers on the red planet with Steve Squyres, Melissa Rice, Andrew Knoll and Michelle Viotti. Plus, we'll test your knowledge about some recent science in the news. First up, a brief state of the rovers report from Cornell's astronomer Steve Squyres. He is the principal investigator for the science instruments on the Mars Exploration Rover Mission. He spoke at a Mars research press conference at the annual meeting of the American Association for the Advancement of Science in Boston in February.

Squyres: Spirit is now hunker[ed] down due to winter. Spirit is deep in the southern hemisphere of Mars and what that means is winter is pretty tough, and so what we've done is we have parked the vehicle on a north-facing slope, tilting the solar arrays towards the sun. Changes occur on the Mars with seasons, changes occur as a consequence of weather systems that come through. Dust could get blown around and sand could get blown around and when the rover is motionless for an extended period of time, you can actually monitor those changes. So, we are going to turn around into a weather station for a period of months, also do other science of the stuff that's getting around us and when spring time comes we are going to continue the exploration. Very briefly, Opportunity: Opportunity has come to (unclear 1:24), drove through the Endurance Crater and then we did this 21-month long slog to the south, hopefully getting eventually to this place that we call Victoria Crater. The geological promised land is under (unclear 1:38). It is a spectacular window into the subsurface of Mars, it's 800 meters in diameter, some 70 meters or so deep, and as we speak right now, our Opportunity is descending down the wall of this crater. The rocks it's really on are layered – they are horizontally layered rocks and you are driv[ing] along a flat plane. You're basically seeing the same rocks over and over again, but if you find a hole in the ground, you can go down into that rock. We didn't bring the drill with us, we didn't bring a backhoe, we didn't bring explosives, but Mars has been kind and has dug these wonderful holes in the ground for us and so we used these as probes at the subsurface. This shows the kind of rock we have here, very finely layered; it's made mostly of sulfate salts. We believe that it formed long ago; water has evaporated away and left the salts behind. This shows the layers that we've been working in recently. Looking down slope, this is the picture that's been taken fairly recently. We're looking down slope and this is the next new layered rock that we hope to get into; it's a layered rock called Gilbert. What we're trying to do is piece together a story from measuring the composition, the texture, the mineralogy of these rocks; and piece together a story of what has happened with water and what are in this location and so both rovers continue to do well and expect more science to come.


Steve: Next up is Melissa Rice. She is still a graduate student at Cornell, but she's been a major player in one of the rover's most important discoveries. We talked at the AAAS conference.

Rice: I'm what's called the payload downlink lead for the Pancam instruments, which are the cameras. There is [are] two of them on each rover and I am often one of the first people to see new images that come down from the rover and I check and make sure that we got all the images that we asked the rover to take and I check and make sure that the camera has been behaving properly, that the temperatures are okay and that our instrument is healthy.

Steve: There was a serendipitous thing that happened with Spirit.

Rice: Right.

Steve: Yeah. You had the broken wheel on it and actually wound up being a really good thing. Why don't you talk about that?

Rice: Yeah. Spirit's wheel broke after we had climbed into these hills called the Columbia Hills and the front right wheel, the motor broke and it hasn't turned since, so we've been driving backward, dragging that wheel behind us through the dirt.

Steve: How long ago did this happen?

Rice: It has been over a year now.

Steve: So you have been dragging that wheel behind you, as if you have hurt your leg and you were dragging it behind you, and you know, instead of stepping down nicely you have the edge of your foot kind of digging into whatever you're walking through.

Rice: Right. And if you're walking along the beach, you are digging a trench in the sand with that dead foot.

Steve: And so, on Mars you end up digging a trench in the Martian soil and you turn the camera around to see where you've been and all of a sudden you see things that you never expected to see.

Rice: And all of a sudden right underneath that top layer of red Martian dirt is this bright yellow, and sometimes bright white, soil that was right underneath the surface, and we never would have seen it otherwise.

Steve: And this bright white soil, I mean, how bright was it?

Rice: It is the brightest stuff we've ever seen on Mars.

Steve: So, you have other instrumentation besides just stuff in the visible spectrum.

Rice: Yes.

Steve: So, you were able to actually do some chemical analysis of these soils?

Rice: Yes. We've several spectrometers and so we were actually able to see what the composition of these soils was and what we found was that the white stuff was about 90 percent pure silica and the yellower stuff had very high sulfur concentrations.

Steve: So, what does that tell you that we didn't know before about Mars and its geology?

Rice: Well, this sulfur material – they are mostly different kinds of sulfate salts which usually form a sort of… precipitates out of bodies of water, or they could be condensation of different materials out of fume gases, so, kind of a hydrothermal Yellowstone on Mars.

Steve: So, that's a really good indication that not only was there water, but there was all sorts of geothermal activity going on in the water.

Rice: Water and energy.

Steve: Water and energy…

Rice: That's exactly what we are looking for.

Steve: And that's a good place to find little microbes, isn't it?

Rice: Perhaps.

Steve: Yeah, I mean, it's no longer there—or it might be there—we don't know, because it will be subterranean.

Rice: Who knows what's deep under the surface, but present surface conditions on Mars now; no bugs are living there now.

Steve: Right. On the surface, but beneath the surface, it's possible.

Rice: There may be micro-niches where that may be habitable, but…

Steve: And the white silica, what does that tell you about the Martian geology?

Rice: Well, when we see that white silica on Earth we usually find it around hot springs. So, we see a lot of it as sinter deposits in Yellowstone, in geothermal areas in New Zealand. And how it forms is either you have a lot of hot steam and water kind of stripping away all other minerals from the rocks – it's called leaching, and everything is stripped away except the silica, which is the least soluble, and it's what is left behind. Or sometimes the silica is deposited directly out of geothermal waters.

Steve: So, hot springs are another place to find a lot of microbes on Earth?

Rice: There are a lot of microbes—thermophiles—that love those hot spring environments.

Steve: So, the wheel breaks and you figure it's a bad thing, but this has turned out to be real boon to what kind of research you're doing up there.

Rice: Yeah. (laughs) Nothing this good happened when I broke my foot.

Steve: This is going to be what you write up for your PhD?

Rice: It might. I propose my thesis topic next year, so I am trying to narrow it down. I am trying to carve a niche for myself in this problem. One of the researchers at Cornell described this new problem of where these bright soils came from as… he compared it to a foul ball being hit into the stands of a baseball game and everyone in the crowd is diving after it trying to get it and that's kind of what researchers in our field are doing now with this new incredibly interesting problem, and I'm one of the fans diving after it.

Steve: Well, good luck I hope you get it.

Rice: Thank you.


Steve: This work has only been announced at meetings, it should be published in the next few months. By the way, the area containing this silica is now known of course as Silica Valley. A little-talked-about aspect of the Mars mission is that, in an important sense, they're just getting started. Harvard's Andrew Knoll is a biologist who is a member of the Mars rover team; he was also at the AAAS Mars press conference.

Knoll: The first thing to say is that while the discovery phase of the Mars mission continues in pace, the interpretation phase is just getting behind and as still, they would agree that for much of the last few years, there was so much work going on a day-to-day basis that the members of the science team didn't really have a lot of time to think about certain implications of what we were discovering. Now, as inevitably, in some ways mercifully, that the rate of movement of the rovers slows down, we are actually able to go back to the data that we assembled over the last four years and try to really mine its richness in greater detail and many other members of the International Science Committee here will agree with that as well.


Steve: There is another mission to Mars that is going to leave Earth next year, the Mars Science Laboratory rover. I spoke with Michelle Viotti from NASA's Jet Propulsion Laboratory about the new rover at the AAAS meeting.

Viotti: Welcome to Mars.

Steve: Well, thank you. We are standing here in the exhibition hall here at the AAAS meeting and you have a model of the next thing that's going to be sent to Mars. There is something that's going to land on Mars before this goes up.

Viotti: Right. On Memorial Day weekend the Phoenix Mars Lander will be landing in the Martian Arctic. And this is the next rover to go to Mars and it will be launching in the fall of 2009.

Steve: And it will get there when?

Viotti: Early 2010.

Steve: Early 2010. And is it going to be more equatorial or more polar in its orientation?

Viotti: Yeah. Actually this rover can access about 75 percent of the planet and right now the scientific community is hotly debating where they want to go.

Steve: So, tell me about this. It's much bigger than the Spirit and Opportunity that are on Mars now.

Viotti: Right. They are about the size of golf carts and this is more car-sized.

Steve: Yeah. It's more like an Escalade (laughs) actually. Tell me about, I know there's—what looks like it would be the head of this robot—there is one big red eye there that's going to be a laser.

Viotti: Right. That's a laser and it has a telescope and what it can do is it can vaporize the surface of rocks from a distance and analyze the plasma cloud and determine some of its properties so that the scientists can determine whether they want to drive over and study it in greater detail.

Steve: Cool, and there is this big arm coming out of the front—looks like it has a shoulder and an elbow and a wrist and a big Swiss army knife of a hand there—that's about a foot and a half across.

Viotti: Right and it works exactly like a human arm does with joints at the shoulder, elbow and wrist just like you said, and that gives it a lot of flexibility and it has several spectrometers on the ends along with some devices that can take rock samples. What this rover can do with its robotic arm and some of its tools, is really look up close at rocks and soil samples and look at what they are made of, but also look for organics.

Steve: And the organics are of particular interest because they are a tell-tale sign that maybe something was alive at one point or…

Viotti: Well, they are actually the chemical building blocks of life, and so what the current rovers are doing are looking for habitats where water once was and what this will do is look and make sure that the right chemicals are there that we know support life on Earth, and if those two factors are there, then perhaps one day we will go back with astrobiology field laboratories to do life-detection experiments, but that's off in the future.

Steve: Also, there is this series of four—they look like gears on the front—but they're really for grinding stuff, right?

Viotti: Right. Those are extra drill bits. So what the rover can do is drill into a rock, take a sample, bring it on board to the chemistry lab and analyze it. And because it could last a lot longer then the single drill bit can, there are extra spares for it.

Steve: Also, it can go up and pick one of those up when one of the drill bits gets worn down.

Viotti: Right. It'll just turn its robotic arm around and pick up a new one and continue on its studies.

Steve: Very cool and they tread on the, well it's hard to say if they are tires or wheels. I am not sure actually. What're you calling them?

Viotti: They are wheels and they are made of aluminum and they do have some holes in them and those treads, basically, by having a different pattern they can tell slippage on the terrain, to really determine how far the rover has traveled.

Steve: Right.

Viotti: If you think of it this way, sometimes, if the wheels turn but they are slipping in the terrain, you might get more wheel turns that would tell you that you have gone farther than you actually have

Steve: I see.

Viotti: So, they can use that change in the tread pattern to understand how far it's really traveled.

Steve: Right. I see, because one apparent length may not be the actual length.

Viotti: Rotation of the wheel.

Steve: Right, that's what I mean.

Viotti: Yeah!

Steve: And what's the… there is a thing up on the right as we are looking at it, that's sort of a misshapen hexagon that looks like a solar panel, but what is it?

Viotti: That's actually is a high-gain antenna. This rover has three antennas and the one you are pointing to is the high-gain; right behind it, the gold post there, is the low-gain and then the nice stripped round-shaped canister…

Steve: …Little barber pole looking thing?

Viotti: Right. Exactly. That's its UHF antenna, which communicates up with the orbiters that then can relay a lot more data back to Earth that way.

Steve: It can also watch Uncle Floyd on channel 68, but that's for the older kids in the audience. What about the power supply, if at all? Is it solar powered?

Viotti: No, it's not. It has a radioisotope thermal generator.

Steve: And how long is that designed to last?

Viotti: It can last a really long time, you know, several years, potentially. This mission design, though—the rover is designed to last for 687 Earth days and that's the equivalent of a Martian year. That's the design and then it could potentially go longer than that. It can last longer than that, yes.

Steve: We've seen that with the other ones. Well, this is great. Thanks very much for talking to me.

Viotti: Sure thing, my pleasure.


Steve: So, lots going on Mars. For more, you can always go the Jet Propulsion Lab Web site,, and you should find a couple of pictures I took of the model Mars Science Lab rover posted with this podcast at

The Mars Science Laboratory Rover:
Credit: Steve Mirsky

Credit: Steve Mirsky

Now it is time to play TOTALL……. Y BOGUS. Here are four science stories, only three are true. See if you know which story is TOTALL……. Y BOGUS.

Story number 1: Microbes in clouds play a big role in snow.

Story number 2: One of the Mars orbiters recently took the first ever photograph of an avalanche on Mars.

Story number 3: Know how your stomach can swell after a big meal? Researchers have identified proteins responsible for that ability of the gut to relax.

And story 4: Shark populations are up, but the number of shark attacks on humans declined last year.

(orchestra plays)

Time is up.

Story number 1 is true. Recent research revealed that single-celled organisms living in clouds seem to serve as nucleation points about which ice can crystallize, leading to precipitation. For more, check out the February 29th episode of the daily SciAm podcast 60-Second Science.

Story number 2 is true. On February 19th, the Mars reconnaissance orbiter got the first picture of an avalanche on Mars near the North Pole. The picture was released on March 3rd and shows clouds of debris near the site of the ice and dust avalanche.

And story number 3 is true. Researchers at University College, London have found two proteins that allow the gut to relax and the stomach to expand to accommodate a big meal. Your stomach can actually get 25 times bigger while eating. Finding where to block the actions of the proteins could keep people from gorging by keeping the stomach constrained. It wouldn't be a diet pill, so much as a "stop, you're full" pill.

All of which means that story 4 about shark populations being up and attacks down is TOTALL……. Y BOGUS. Because what is true is that shark numbers are in decline, but their attacks on Earth have risen. Here's why: because our population is up, more of us spend more time at the beach and we frequent the shallow waters that sharks prefer. So, we increase the odds of getting bit. That's according to our friends at Still, there were only 71 shark attacks on humans in 2007, up from 63 in 2006. Sharks killed one human in 2007 and one more so far this year. Humans killed 38 million sharks last year. (laughs) And you are afraid of them!!!!


Well, that's it for this edition of the weekly SciAm podcast. You can write to us at and check out numerous features at, including the SciAm video news feature, currently searching for a new name, as well as a lot of other stuff. For Science Talk, the weekly podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.

You know when that shark bites with its teeth, babe
Scarlet billows start to spread
Fancy gloves though, wears ol' MacHeath, babe
So there's nevah, nevah a trace of red.

Science Talk is a weekly podcast, subscribe here: RSS | iTunes

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