The following questions were answered by astronomer Dr. Cathy Imhoff of the Space Telescope Science Institute.

What kind of material is Mars made of?
Mars is made up of rocks pretty similar to Earth, as far as we can tell. There are some differences though. There is a lot of iron in the surface rocks, which is why it looks red (like rust). There are also more silicate-type rocks and less carbonate-type rocks than on Earth.

What is the atmosphere like on Mars? Could a human breathe there?
Mars is smaller than Earth, so it can't hold on to much of an atmosphere. The air is mostly carbon dioxide, with a little nitrogen, argon, and oxygen. Definitely not enough to breathe!

How often does Mars rotate?
Mars rotates once every 24 hours, 37 minutes, 23 seconds — almost the same as Earth.

What is the temperature on Mars?
Mars is over 50 percent farther from the sun than Earth, so it receives less than half as much sunlight. This, plus the thin atmosphere, makes Mars pretty cold. It can get as warm as 80° Fahrenheit, but usually it is much colder, as cold as –200° Fahrenheit!

How far away from Earth is Mars?
Mars'orbit is about 1.5 times Earth's orbit. So if both planets were on the same side of the sun, at their closest point they would be about 46 million miles apart. But if Mars is on one side of the sun and Earth is on the other, Mars is 233 million miles away!

If the gravity on Mars is less than on Earth, how do things like equipment put on Mars not float off?
The gravity on Mars is less than on Earth, but not zero. It is still enough to hold the planet together and things stay on the surface. Have you seen pictures of astronauts on the moon? The gravity is even less there. This meant that they could jump high and things weigh less, but there was no danger of them jumping so high that they would never come down again!

Is it true that Mars is in a full vacuum?
Not really. Mars has a thin atmosphere. It wouldn't be enough for us to breathe but it's not a vacuum.

Does Mars have any other unknown planets surrounding it?
Mars has two very small moons, which are probably asteroids that came close to the planet and were captured by its gravity. We have studied Mars pretty closely so I don't think there are any other moons, rings, or whatever that haven't already been found.

Why does Mars have canyons? Does it have many canyons?
Mars does have many canyons. Some of canyons look like ancient river beds. So many astronomers think that at one time, there was water on Mars. But now most of the water is frozen ice at the north and south poles of Mars. There are no rivers or lakes. But millions of years ago, there might have been! Some of the other canyons are cracks in the rocks, not due to water.

What are the clouds like on Mars?
The clouds are made up of water ice (there are other kinds of ice too). They are like cirrus clouds on Earth, but often they form an icy fog close to the ground. There are some really neat pictures taken by the Viking orbiter that show icy fogs rising from inside Martian craters as the sun rises during the morning!

What are the inside layers of Mars like?
Mars'surface soil is pretty similar to Earth's but of course without the organic matter (decomposed leaves, etc.). Chemically the soil is mostly silicon and oxygen combined with metallic elements such as iron and magnesium. The grains of soil appear to be coated with iron-oxide rust, which is what gives Mars its reddish hue. I don't think we know much about the lower layers. The Viking landers only scratched the surface.

When you dig in Mars, does it get hotter like Earth or colder?
I think that if you go very deep inside of Mars, it will get hotter. This is because the pressure of the weight of the rocks above will make the rocks below hot, just as for Earth. This should be true for any of the planets.

Are there dust storms on Mars?
Yes, there are big dust storms. Sometimes the dust storms get so big they nearly cover the whole planet, making it hard for us to see the surface. Now that's a dust storm!

Is there any possibility that there is or could have been life on Mars at one point in time?
It seems possible, since there seems to have been some liquid water on the surface of Mars in the past. We can see what appear to be dry river beds on the surface of Mars in pictures taken by Viking. One of the major goals of landing a satellite on Mars is to search for evidence of life, or extinct life, on Mars.

Is it possible to heat up the climate of Mars so that human beings would be able to live there?
There are some scientists who have studied how we could "terraform" Mars so that people could live there. From what I have read, it could be done but it would cost incredibly huge amounts of money. (My own opinion is that we should learn how to live properly on our own planet before we mess around with another one!).

When will we be able to put people on Mars?
I am not sure when we will be able to put people on Mars, but I would guess it won't be for at least another ten years. There have been suggestions that the United States and Russia will team up to send astronauts and cosmonauts to Mars, but no one has actually said they will definitely do it. There are some difficult problems to overcome too. It would be a long trip. How do we supply enough food, air, etc. to last for many months? How will people be in weightlessness for so long? Our experiences with the Russian space station Mir have helped us learn about these things.

What would it take for people to ever live on Mars?
Mars would be a tough place to live, but then so is Antarctica. It is cold; many days the temperature would not get above freezing (32°F). The air is quite thin, so people would have to have air tanks to go very far. You might be able to build a big dome that would work like a big greenhouse to keep air and warmth inside. You'd need extra lights to help plants grow, because the sunlight would be less than half of the light we get on Earth. You might be able to get water from the icecaps. That could be used both for water to drink and to water the plants and also could be used to generate oxygen to breathe (the plants would help too). I don't know if such a colony could become completely self-sufficient, not needing anything from Earth.

Is there liquid water or frozen water on Mars?
There is indeed water on Mars, mostly in the form of snow and ice. If you look at a picture of Mars, you will notice that it has ice caps at the north and south poles. We also know that there is water on Mars from some pictures taken by the Viking Orbiter back in the late 1970s. In some of them you can see fog rising from inside Martian craters in the morning when the sun first shines inside of them! We think that the fog is actually ice fog. (We sometimes get ice fog on Earth too. Just ask my friend who lives in Fairbanks, Alaska!) Another place there might be water is down in the soil in the form of permafrost. However, that is only a guess at this time. We don't see liquid water on Mars because the air is too thin. But at one time there may have been rivers on Mars. Some of the channels we see on the surface of Mars have all the characteristics of river channels seen on Earth. So you might have to get your water from the polar caps, but there should be enough for a small colony.

What type of power sources are available on Mars?
Let's think about the possibilities for a power source. There is no water for hydroelectric power, no coal or wood, and probably little geothermal power. I don't think we want to try to set up a nuclear power plant either. Wind power might be a possibility. We often see dust storms on Mars. Solar power is probably the best choice, although Mars is further from the sun, so you would need solar arrays more than twice as large to generate as much solar power!

Are there robots on Mars? If so, how many? What is their purpose? How long will they be there?
There aren't any robots operating on Mars yet, but NASA has some planned. They include small rovers that will sample the soil and look for signs of life. I will see if I can find some details; there are several Mars missions in progress or planned over the next several years! In the past we had two Viking missions to Mars. Viking 1 landed on Mars in 1976. It didn't move around but it worked much like a robot. The lander took a number of pictures, analyzed the atmosphere and the soil, and took many other measurements. Another part of it, the orbiter, stayed in orbit around Mars and took more pictures and measurements. That summer I was working at Lowell Observatory and got to see many of the orbiter's pictures right after they were transmitted back to Earth. It was very exciting! There was also a second Mars orbiter and lander, called Viking 2. That lander landed in a different spot on Mars.

Is there really a "stone face" on Mars?
There is a feature that, when the sun shines at the right angle, looks like a face. But when the sun shines on it from a different angle, it doesn't look like a face anymore. Back in 1976, I worked at Lowell Observatory and we were getting the new pictures from the Mars Viking Orbiter. It was very exciting. One of the guys would go through the pictures (there were thousands!) and put the interesting ones up on the bulletin board. There are several odd-looking features like the "face." I remember one that looked like a giant amphitheater, with concentric rings of "seats." But the "amphitheater" was probably about 50 miles across, and the "seats" 5 miles across. We believe that these are just natural features that our human eyes and brains "see" as faces, etc. This is much like similar features on Earth. Down in Arizona near where Geronimo lived, there is a mountain named for him because when you look at it from a certain angle, it looks like a profile of a Native American's face.

Are there any plans to have a satellite orbit Mars like the one that is orbiting Jupiter?
Yes, we sent a Mars Orbiter a year or two ago, but unfortunately it malfunctioned just as it got to Mars. A new Mars Orbiter is being worked on. I'm not sure when it will be launched, probably in the next year or so.

How would you feel about traveling to Mars? How long will it take?
I would love to visit Mars — it would be very exciting to explore the planet! But I wouldn't want to live there. We would have to take along almost everything we need to survive — air, water, food, shelter. It's a long way to Mars. How long it would take to get there depends on how you traveled. Let's see — at its closest Mars is about 45,000,000 miles away. If we could drive a car along a highway to Mars (!!?!) at 65 miles per hour, it would take 79 YEARS! The space shuttle travels at a speed of about 260 miles per MINUTE. Even so the shuttle would take 120 days to get there. In reality, we can't go straight to Mars. We take a curved path, and it would take roughly six months. Now that's a long trip!

What are some interesting facts about Mars?
There's a neat article on the soil of Mars in Mercury magazine, which is published by the Astronomical Society of the Pacific. Here are some highlights.

  1. The Viking 1 Mars Lander set down on Mars. It took numerous pictures of the surface, tested the soil, and measured the weather of Mars.
  2. The air is so thin that a 50-mile-per-hour wind storm would feel like only a 4-mph breeze here on Earth.
  3. The surface of Mars is weathered due to extreme temperature changes and from frost. There is a little water, about 1 percent, in the Martian rocks. This has broken the rocks down into fine particles of soil that can get whipped up into dust storms.
  4. The Mars Viking lander dug only about 4 inches into the soil. So we don't know much about the deep soil. There is no evidence for organic material (life!) in the surface, but that may be because of the sun's strong UV light (Mars doesn't have an ozone layer to protect it). If life ever grew on Mars, the evidence may be buried deeper in the soil.
  5. Everything we need for life exists on Mars (oxygen, nitrogen, water) but we would have to "work" the soil a lot before we could grow plants. First, there seems to be hydrogen peroxide in the soil, which would poison anything (we use it here for an antiseptic). Also there are no plants to fix nitrogen into the soil. There are also a lot of salts in the soil that would have to be leached out. But it could be done!