Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science
scientists from previous shows
cool careers in science
ask the scientists
PREVIOUS
SCIENTISTS

Photo of Kathie Thomas Keprta Journey to Mars:
Why Go To Mars?

Kathie Thomas Keprta


q Dear Dr. Kathie, Your job sounds very interesting. You are very lucky that you get to handle the rocks that fell from Mars. What do you think people be studying on the surface of Mars, besides looking for bacteria and signs of plant life?

A You are right that we need to be studying more than just whether or not Mars had or still has evidence of past life or if present life still exists on the planet today. However, this is such a fun topic and is so very interesting that we wish to answer the question "are we alone in the universe?" Other topics we will be studying include the following below:

1. How did Mars form? Is it different from Earth?

2. Why did Mars become dry and barren when it apparently had lots of water on the surface and an atmosphere like our Earth billions of years ago?

3. Did Mars have a magnetic field like the Earth does now?

4. What is the composition of the rocks and what can they tell us about how Mars formed?

5. Can humans survive on Mars? What types of special equipment do we need to live on Mars? What will living on Mars teach us (for example, how do human bodies respond to reduced gravity over time?)?

6. Can we produce special products on Mars (for example special types of plants that like to grow in reduced gravity or certain types of crystals used in computers)?

7. Are there minerals on Mars that we could use on Earth or use to support humans living on Mars?

There are many technical and engineering questions to answer in addition to science questions. Of course, we are so interested in life on another planet because if we do find bacteria living under the surface of Mars now, do they have special proteins or enzymes that might help us fight cancer or AIDS? Life on another planet may help us understand the chemical and physical processes associated with life here on Earth.




q As a planetary geologist, what kind of experiment would you design for the astronauts to conduct on a mission to Mars?

A This is such a neat question because there are so many questions that need to be answered! I am so interested in finding evidence of existing life on Mars so I would want an experiment that would detect the presence of organisms alive today. This is a problem because we think that if there is water on Mars then it is probably under the surface. Why do we care about water on Mars? Because life on Earth needs to have water! So if there is water deep under the surface of Mars then there may be life deep under the Martian surface. The experiment would need to include a way to reach samples deep under the Martian surface.

Did you know that we are finding the same thing on Earth? We know that deep under the Earth's surface are bacteria that don't need sunlight to live. Some of these bacteria live in places where there is little to eat, so they replicate very slowly and live very long life spans (even thousands of years!). We may find the same thing on Mars. My experiment would include collecting samples from deep under the Martian surface, then examining the rocks for organisms (probably using some sort of microscope), and maybe trying to determine the RNA or DNA composition of the organisms. With the new technology that will become available within the next ten years maybe we can send a microscope to Mars!




q Why do you take so many precautions when working with the meteorite? I assume it's so it doesn't get contaminated. Have you been successful? Is the fact the rock may have been contaminated on Earth part of the controversy that surrounds it?

A Thank you for this question. YES! Contamination of meteorites we find on Earth is a very important concern for those of us working with these samples. As most of you know, we find most of our meteorites in Antarctica. We send groups of people to pick up meteorites for about 8 weeks each year. Commonly they can collect between 500 to 1000 meteorites during that time. Meteorites in Antarctica are often found to be less weathered (or contaminated) by being on Earth than meteorites found in other places. This is because they are embedded in ice for many years and not exposed to rain, warm temperatures, lots of bacteria, and plants, etc.

If a meteorite was found in Houston (where I work), it would be very likely that this Texas meteorite would be highly contaminated compared with one from Antarctica. This is true for the Mars meteorites as well. Of the 13 meteorites from Mars, nearly half of them come from Antarctica. The meteorite that we looked at and found possible signs of Martian life was called ALH84001. This meteorite came from the Allan Hills ice field (ALH) in Antarctica and was picked up in 1984. At that time we didn't know it was from Mars; a scientist here in Houston determined in 1994 that ALH84001 was from Mars. We began studying this rock in 1994 by looking at the outside of the meteorite. Usually, if we have a lot of terrestrial weathering (for example if we see salts or rust forming on the outside of the meteorite) then we think that this meteorite could be contaminated. We got very lucky with the Martian meteorite ALH84001 which turned out to be relatively free from terrestrial contamination. Only a few salt crystals were seen on the outside of this meteorite. Therefore we think that the minerals we see on the inside of the meteorite were formed on Mars.

We are now measuring things we cannot see. For example, we found organic compounds in ALH84001 called polycyclic aromatic hydrocarbons. We have made a strong case that these organic compounds are from Mars. Others have analyzed the same meteorite and have found different types of organic compounds called amino acids. They believe the amino acids are not from Mars but are from Earth. So we find that the meteorite has two types of completely different types of organic compounds-one from Mars and one from Earth. That is great! We know that one type of organic compound is Martian and that is exciting! However, we must be careful in looking at meteorites from Antarctica. We can help to solve this problem in two ways:

1. We can look at Mars meteorites that were not found in Antarctica (for example one is from Libya, another from Egypt and so on). They will probably be contaminated in other ways but they will help us determine the type of contamination from Antarctica.

2. We can get samples from Mars and try not to contaminate those when we pick them up.

Hope this helps and lets you know that studying meteorites can be very complicated (but FUN too!). It is like a puzzle where it seems like all the pieces don't fit together, but with enough time they will fit and you will be able to make out what the puzzle means.




q If Mars was once covered in water, what happened to it? If it's under ground, why and how did it get there and what happened to the oxygen that the evaporated water left behind?

A I believe that your questions are what happened to the possible water on Mars? What happened to the atmosphere on Mars?

Water: We have images from the Mars Pathfinder and Mars Global Surveyor which strongly suggest that water played a major role in the history of Mars. We believe that water was responsible for the presence of valley networks and numerous possible indicators of ground ice that we see today. The fate of these waters is controversial. One suggestion is that the floods formed lakes which froze solid. Then more floods on top of these frozen lakes would also freeze leaving thick permanent ice deposits in the northern plains of Mars. This water was permanently removed from the global aquifer system so that flooding eventually stopped. Another suggestion is that ocean-sized bodies of water accumulated and they temporarily altered global climates. The oceans eventually disappeared leaving behind shorelines.

Mars has many craters on its surface. It went through a period of time in which it was heavily bombarded by meteorites and comets. We think that after all those impacts, Mars still had a few hundred meters of near-surface water and at least 100 meters flowed across the surface in large floods. The fate of these waters is uncertain. Some was lost from the upper atmosphere, some may be in the polar terrain, and some may be in the permanent ice deposits in the low lying northern plains and elsewhere.

Atmosphere: Mars has a very thin atmosphere as detected by both Viking and Pathfinder missions. It mainly contains carbon dioxide and nitrogen with a bit of carbon monoxide, argon, trace amounts of oxygen and water (which will vary depending on the time of Mars day). The pressure is about 1/100 of that on Earth. In the past we believe that the atmosphere may have been more like that of Earth's, even with the possibility that more oxygen could have been there. Like the question of where did the water go, we are uncertain what happened to Mars atmosphere.




q From the program I watched, you claimed that Mars did have an atmosphere at one time. In the future if we plan on setting up colonies there, could the planet be brought back to the point of supporting an atmosphere again? How would you begin the process?

A The problem with bringing back a more dense atmosphere on Mars (the present atmosphere is about 1/100th of that on Earth) is Martian gravity; the gravity on Mars is only about 1/3 of Earth's. Without an earth-like gravity, a substantial atmosphere could not be maintained on Mars. But if we used something like a bubble with ultraviolet radiation protection, then maybe we could produce an atmosphere in the bubble which could maintain human life and with enough pressure, maybe even liquid water could exist in ponds within the bubble. Even if Mars could maintain an atmosphere, it would take a VERY long time to produce one that could sustain human life. It would be nice if it worked like scenes from the movies; in the movie "Total Recall", a Martian atmosphere was produced instantaneously. Unfortunately, it is much more difficult, if not nearly impossible in real life.



q At this point what do you know about the composition of the rocks and soil on Mars?

A The first analysis of Martian soils took place over 20 years ago by Viking. Then the Pathfinder mission landed on Mars in 1997. Do you remember the vehicle called Sojourner which roamed the Martian surface and analyzed rocks called Scoobie Doo and Barnacle Bill? We have found that the rocks analyzed by Pathfinder contain a lot of an element called silicon. It has been suggested that rocks with high amounts of silicon are probably andesites. One way andesites can form is when liquid, hot rock-material from the mantle intrudes deep within the crust. Crystals rich in iron and magnesium also form but are separated from the melt, leaving a more silicon-rich melt that erupts onto the surface. This composition is very different from the Martian meteorites we have studied; the meteorites are composed of relatively low silicon and are high in iron and magnesium. The meteorites are believed to have formed by partial melting of the upper mantle of Mars; the melt rises up through the crust and solidifies at or near the surface. Both of these types of rocks formed at high temperatures.

However, not all of the Martian rocks are believed to have formed at high temperatures. Some rocks appear to have layers like those in terrestrial sedimentary rocks, which formed by the deposition of smaller rocks in water. Some of the Sojourner images show rocks which appear to be rounded suggesting erosional activity by water on Mars. There are carbonates (carbon-containing rocks) in some of the Martian meteorites. Carbonates in Martian meteorite ALH84001 are believed to have formed at low temperatures with water and possibly bacteria, too. Therefore, there are several different types of rocks from Mars, some formed at high temperatures and some believed to have formed at low temperatures. Of course we have analyzed only a very small number of rocks from Mars. To get the complete story of how the planet formed, how much water was there, if bacteria existed or still exists on Mars, we need to bring back rocks and examine them with more sophisticated types of equipment that we have here on Earth. I believe that if we plan well (plus a bit of luck) that we may get samples back from Mars as early as 2008. If you are really interested, then study hard and you will be prepared to help us discover new and exciting information about the red planet!




q How will we go about finding out if there is water under the surface of Mars? We will dig to find it, or use more sophisticated techniques?

A You are right! If we are going to find water on Mars, we will have to look under the surface. It will be difficult to drill for Martian water though. A better idea would be one that will take place in December 1999. Two basketball-sized areoshells will crash onto the Martian surface at about 200 meters/second. They will punch a hole in the Martian soil of about 2 meters deep and release probes that will try and determine if water ice is present below the Martian surface. Unfortunately, it would be great if the probes would go even deeper. No one knows how deep we would need to go to find water under the Martian surface.



q Will the Martian meteors eventually be put on display in a museum so everyone see them?

A There are several Martian meteorites on display now at the Natural Museum of Natural History at the Smithsonian Institute in Washington D.C. If you have time, take a trip to D.C. and visit this museum; the exhibits are wonderful and there are many types of meteorites you can see there! We also have several of the Martian meteorites at NASA Johnson Space Center in Houston, TX. Sometimes pieces of one Martian meteorite go on display at Space Center Houston (just down the street from NASA). Most meteorites from Mars are relatively small. However, one Martian meteorite called EETA79001 was huge; it weighed about 8000 grams. Two pieces from this meteorite are available for display and weigh about 33 and 259 grams for a total weight of ~300 grams. So you see that most of the meteorite (~7700 grams) was reserved for scientists to study. We keep our Martian meteorites in nitrogen cabinets so they are not exposed to Earth's atmosphere and possible contamination. That means that the meteorites are kept "clean" so at any time they can be examined by scientists who want to learn more about Mars. We now have 13 meteorites from Mars and we are hoping to add to that number. About half of the Martian meteorites come from Antarctica and we send teams to pick up more meteorites every year. Hopefully we will find more meteorites from Mars in Antarctica.



q My favorite part was NASA'S WAY TO MARS! I have a question on that story. Donna Fender showed Alan Alda a piece of Mars. Do pieces of Earth also fly into space?

A Many years ago, scientists thought that we couldn't get pieces of Mars to come off of the planet. About 20 years ago, we discovered our first meteorite from Mars and then realized that pieces (or what we call meteorites) of Mars could be ejected from the planet. We believe that impacts by comets or asteroids can force pieces of Mars into space. These pieces need to be going really fast to get away from Mars, about 5 kilometers / second. Well, because we have found meteorites from Mars on Earth, many scientists believe that it is possible to also have pieces of Earth fly into space when comets and asteroids impacted our planet many, many years ago. The escape velocity for pieces of Earth are about 12 kilometers/second (compare that to Mars), so it would be more difficult, but probably not impossible to get chunks of Earth into space.



q Do you think the ice on Mars could be converted to water that will be useful to the habitats on Mars?

A The ice on Mars is not the frozen water ice that you find here on Earth. This ice on Mars is believed to be composed of carbon dioxide. So we couldn't use that type of ice to make water. It may be that our best chance for finding water on Mars may be under the Martian surface or under the ice.



q I am a science teacher at Sultan Middle School in Sultan, Washington. You are a great role model for female science students. In your busy schedule, do you have the chance to send my students a brief message about why you choose your career? Thank you.

A Dear Sultan Middle School,
I think that I have the best job in the world. That job is to ask questions and try and answer them. I always thought that studying science was just OK when I was in middle and high school. The reason is that when you are young you need to understand some of the basics of how science works. For example, you can't really play football until you understand the basic rules of the game; science is just like that. However, learning rules can be a little tiresome. But once you understand some of the science rules, then you can apply those rules and explore new things. That's when studying science gets really FUN! You begin to look at things no one else has ever looked at. Imagine being in a laboratory with a microscope. You put a piece of a rock under the scope so you can look at it more closely. But you are not looking at just any rock. This is your first look at a piece of Mars! No one has ever looked at this rock before or has seen the things you see while you look at this rock. It is very exciting. Not only with rocks; some scientists are trying to find cures for cancer or AIDS and they are also very excited about their work. I guess that the most important goal to have about your future careers is to know that you can learn and grow and be very excited about getting up and going to work in the morning. Science has so many questions to answer in so many different fields of study and the bottom line is that it is really fun!




q Can you please explain the numbering system you use to identify the different Mars meteorites. Did you come up with this system?

A No, I didn't come up with this system of naming meteorites. We have a nomenclature committee which actually decides the names of meteorites but they use a couple of rules. For example, meteorites that are not from Antarctica are named after the nearest post office (nearest to which they were picked up). Meteorites from Antarctica are named after the geographical area from which they were picked up. For example meteorite ALH84001 is called ALH because it was picked up in the Alan Hills (or ALH) ice field. Once the meteorites are picked up from the ice, they are given field numbers and scientists take notes describing the meteorite.

Then the meteorites are sent to NASA in Houston, Texas where once in the lab, they are categorized into groups and further described. The original meteorite descriptions from the preliminary examinations of meteorites are published in the Antarctic Meteorite Newsletter which is a magazine issued by the Meteorite Working Group to inform scientists of the basic characteristics of specimens recovered in Antarctica. This magazine can be obtained from the Planetary Material and Missions Branch at NASA Johnson Space Center. The Smithsonian Institution also publishes meteorite descriptions and results of field investigations. For more information on meteorites from Mars see the website at: http://www-curator.jsc.nasa.gov




 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.