Students can also make up their own Challenge Questions for each other. These are known as Student Stumpers and examples can be found in the Kid's Corner

Question:

What five features make Mars most like Earth? And, what five features make Mars most unlike Earth?

We hope students will come up with some geologically correct answers, but also with some clever, provocative and tongue-in- cheek comparisons!

ALIKE:

• atmosphere: though Mars' is much thinner than Earth's
• weather: Mars has frost, clouds, but in the current epoch no "precipitation"
• channels that seem to have been carved by running water
• Grand Canyon and Vallis Marineris
• Earthquakes and Marsquakes
• impact craters
• volcanoes
• night and day
• fossil evidence of past life (this will only be accepted if students say it's "definite" for Earth, "possible" for Mars, reflecting continuing scientific debate about what the features in ALH 84001 really mean!). See below, Different!!!

  DIFFERENT:
  

• liquid water
• plate tectonics: though there are Marsquakes, the mighty volcanoes show that the crust has sat over long-lived lava hot spots, rather than riding over them, and forming features like the chain of islands we know as Hawaii
• no ozone layer on Mars protecting the surface
• no large, surface life (plants/animals) on Mars compared to Earth
• Mars' day and year are longer than Earth's
• Vallis Marineris was formed by rifting, not carved by a river, as was the Grand Canyon
• fossil evidence of past life (but this will only be accepted if students say it's "definite" for Earth, "possible" for Mars, reflecting continuing scientific debate about what the features in ALH 84001 really mean!) See above, Alike!!! - no students participating in Live From Earth

Question:

BRUSH UP ON YOUR GREEK!
There is a letter of the Greek alphabet that is very important both to launching NASA's current Mars missions and to getting to Mars. What is that letter? Also, explain how it is used.

Both Mars Pathfinder and Mars Global Surveyor were launched aboard Delta II rockets from Cape Canaveral. "Delta V" is what rocket scientists call the "change in velocity" that keeps a spacecraft on course for a distant planet. Trajectory correction maneuvers fine tune the route by a combination of precise timing, and carefully controlled "burns" providing additional velocity in specific direction.

Question:

GO TELL IT ON THE MOUNTAIN
Olympus Mons is the highest feature on Mars. What is its counterpart on Earth? Be forewarned: it is not Mount Everest! If you think about how astronomers measure the height of features on Mars, you'll have a clue to help this question. What do we mean?

If you measure Mauna Kea, Hawaii, from ocean floor to peak, you will find that it is higher than Mt. Everest, Nepal -- about 30,000 feet compared to Everest's 29,000 feet.

For Mars, astronomers use the "datum level" -- the reference surface at which atmospheric pressure is 6.1 millibars (the pressure at the triple point of water) -- to give a baseline for measurement of altitude. On Earth we use sea level, but that would currently be impractical to do on Mars -- though some astronomers think there may once have been an ocean on Mars, or at least lakes of liquid water, now lost to space or locked in permafrost.

Question:

DIFFERENCES & SIMILARITIES -- CAN YOU NAME THEM?
Discount (ignore, forget about...) one feature that makes Earth unique among the planets (but maybe not the moons) of our solar system, and Earth and Mars are almost identical in a certain aspect.

What do you have to take away from Earth? In what way are Earth and Mars then alike?

If you discount Earth's OCEANS, then the surface area of Earth and Mars -- the dry land of Earth and the surface area of Mars -- are almost the same. (509,600,000 km squared) (Source of surface area: The Cambridge Fact Finder)

Bonus Question

What do we mean when we say that "this feature" may make Earth unique when compared to other planets (but maybe not the moons) in our solar system?

Bonus Answer

Many astronomers think that Jupiter's moon Europa may hide an ocean of liquid water under an icy crust, making it the only body in our solar system, apart from Earth, with liquid water. The Galileo spacecraft is continuing its successful exploration of the Jovian system, and has seen what looks like pack ice, forming then breaking up and reforming in characteristic patterns.

Question:

WHO ARE THEY?
Mars has always been a place that has engaged our imagination, as well as our scientific curiosity. In the 19th and 20th centuries two men with almost the same last name created the exact same titles in two different media. Who were these men and what did they write and produce?

In 1898 H.G. Wells wrote the 17-chapter novel "The War of the Worlds." Forty years later, Orson Welles adapted the novel for radio and on the night before Halloween in 1938, he starred in a radio drama by the same name. This began the most stunning single program ever broadcast on radio. It set off a wave of mass hysteria as Welles described in breathless radio news bulletins and on-the- scene reports that Martians had invaded New Jersey. Even though CBS made four announcements during the radio show that it was "only a play," may listeners did not year them. Panic swept through New Jersey as people fled their homes and covered their faces with wet handkerchiefs to protect themselves from the reported poison gases!

Question:

If geology is the study of the Earth (from the Greek geo-earth and logos-knowledge) what should we properly call the study of Mars?

Your answer can be either etymologically correct, with Greek derivation, or more humorous if you like!

Answer

Areology - Ares is Greek for Mars, just as Geos is the Greek word for Earth. (Remember Pathfinder will land in Ares Vallis, the Valley of Ares.)

Dave Bogan -- 8th grader at Taylor Road Middle School -- Alpharetta, Georgia -- gave the exact answer!
Honorable Mention: Matt Bohnhoff and MESA Class of Provo, Utah.

Question:

The Mars Global Surveyor (MGS) took off in November and is scheduled to arrive at Mars between Sept. 11 and Sept. 22, 1997. The Mars Pathfinder (MPF) takes off sometime in December. No matter when it leaves, it is scheduled to arrive on July 4, 1997.

Why does the Pathfinder get to Mars earlier, even though it leaves later?

And how can the Pathfinder have an exact arrival date even though its liftoff date may vary?

Answer from Cheick Diarra:

There are several reasons for Pathfinder's earlier arrival at Mars. Pathfinder is much smaller and lighter than Mars Global Surveyor. As a result, the rockets sending it to Mars can get it going at a faster velocity. Also, Pathfinder goes on a much more direct route to Mars than MGS, which takes a longer, more looping path. So not only is MPF going faster, it has less miles to travel.

There is a good reason for MGS's more looping path. The arrival velocity depends on the type of trajectory. The more looping trajectory provides a slower arrival velocity. Since MGS is an orbiter, NASA wants it to arrive at Mars with as little speed as possible. This is because it will need to be slowed down with a retro burn to be captured by Mars's gravity. That maneuver is called the Mars Orbit Insertion maneuver, or MOI for short. The slower MGS is going relative to Mars, the smaller the retro burn. And a smaller retro burn means less fuel (and weight and dollars). So that is why MGS is on a more looping trajectory which will allow for a slower arrival speed. MPF, on the other hand, is not going into orbit, so it can arrive at a faster speed, and thus its more direct route to Mars.

To help understand why a more looping trajectory results in a slower arrival speed, consider a golf ball being putted on a slanting green toward the hole. A golfer can hit the ball hard right toward the hole and the ball will arrive relatively quickly. Or else, the ball can be putted more gently toward the uphill side of the hole; in that case, the ball will loop down towards the hole and arrive at a slower speed.

Finally, about the issue of the fixed arrival date for MPF. When we travel to Mars, we have the opportunity to do Trajectory Correction Maneuvers (TCMs) that let us correct not only our aim point at Mars arrival but also the time of arrival. Early on, NASA decided July 4 would be a good day to arrive. This was partially historical. In 1976 when the Viking spacecraft went to Mars, it was expected to land on July 4 for national reasons (July 4 is America's Independence Day). But when Viking arrived, there was a raging dust storm that prevented this scheduled landing so the team missed a July 4 landing and decided to remain in orbit until July 20 (July 20 is the anniversary of the first Apollo landing). So this time NASA has decided that Pathfinder should land on July 4. The TCMs for Pathfinder will be performed to remain true to the July 4 landing date.

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Question:


The largest crater on the larger of the two Martian moons, Phobos, is named Stickney. Ms. Stickney was not an astronomer but she played a critical role in the discovery of the Martian moons. Who was Ms. Stickney and why did she have this prominent surface feature named after her?

Answer from Bill Gutsch:


The two moons of Mars were discovered by astronomer Asaph Hall at the US Naval Observatory in 1877. According to the story, after many nights of searching for satellites that might be in orbit around Mars, Hall was ready to give up. His wife, however, encouraged him to give it "one more try." That night, Hall found Deimos and Phobos, the two Martian moons. In honor of her encouragement, without which Hall might not have made his discovery, astronomers in the 1970s decided to name the largest crater on Phobos "Stickney" -- Mrs. Hall's maiden name.

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Question:


Sometimes the winds on Mars can blow at hundreds of miles per hour and kick up giant dust storms that blanket the entire planet. Yet, if you stood on the surface of Mars at one of these times, you would probably not be blown over. Why?

Answer from from Bill Gutsch:

Martian winds can be swift but the Martian air is so thin that it packs very little punch. In more scientific terms, this means that there wouldn't be nearly as many air molecules striking you per second in a Martian wind storm as there would be in a similar storm on Earth. Far fewer molecules translates into much less pressure (force per square inch) pushing against your body. Such "thin winds" can still create giant dust storms, however, because the Martian surface dust is very, very fine and so can easily be lifted into the Martian sky.

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Question:


Mars has two moons: Deimos and Phobos. If you stood on the surface of Mars and looked up into the night sky, you would see Deimos slowly travel from east to west across the sky while Phobos would be slowly traveling from west to east. In other words, the two Martian moons travel in opposite directions across the Martian sky. Yet both moons actually orbit Mars in the same direction.
Explain this apparent paradox.

Answer from Bill Gutsch


The closer a satellite (natural or artificial) is to the planet it orbits, the faster it travels around that planet. Both Martian moons travel around Mars from west to east. Deimos, however, is sufficiently far from Mars (like the Earth's moon is from Earth) that it travels around the planet slower than Mars rotates on its axis. Thus, to an observer on the surface of Mars, Deimos appears to be "left behind in the sky" and appears to move from east to west. Phobos, on the other hand, is much closer and actually orbits around Mars faster than Deimos.

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Question #11:

Question:

The Valles Marineris is much larger and deeper than the Grand Canyon in Arizona. Yet, if you stood at the rim of the Valles Marineris, it probably wouldn't seem as impressive to the eye. Why?

Answer from Bill Gutsch


While the Valles Marineris is big, deep and wide, Mars is a much smaller planet than Earth. This means that on Mars, the horizon curves out of the way much closer to you than it does on Earth. The result is that differences in elevation in surface features are not as impressive. On Earth, for example, you can stand at the North or South Rim of the Grand Canyon and see the whole breadth of the canyon -- all the way over to the opposite rim. In places, however, the Valles Marineris is over 100 miles from rim to rim. This is so great compared with Mars's tiny size that if you stood on one rim of the Valles Marineris, you wouldn't be able to see the other rim because it would be out of sight over the horizon!

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Question:


Let's say you have just been appointed Baseball Commissioner for Mars. You would like the game to be similar in difficulty to the game as played on Earth. With that in mind, how far back should you place the center field fence (so that it is just as hard to hit a home run).

Assume that a center field fence on Earth is 410 feet from home plate.

Answer from Alan Federman, NASA Ames:

As a first approximation, we need to look at the relevant equation:

F = MA: Force is equal to Mass times Acceleration.

The acceleration we are interested in is due to the gravity field of Mars. Mars gravity is equal to 0.38 of Earth's, so as a first approximation, the "A" on Mars is .38 * 980 cm/s/s = 370 cm/s/s. If the Force of Gravity were the only effect on the ball, 410 ft / 0.38 = 1079 feet (or 323 meters).

To make the game "play the same," other factors need to be considered. For example, atmospheric effects. The thin atmosphere means less air resistance so balls will carry farther. How fast people can run wearing space suits would also be a problem. Maybe changing the mass of the players and their equipment is an option.

While rain-outs are not going to be a problem, games may need to be called on account of wind or sandstorms!

Good Luck, Commish!

Answer from Bryan Glenn:
The old baseball Commish will have quite a problem on his hands placing that fence in the right location. There are actually 2 variables he will have to consider, gravitational differences and atmospheric differences. Both will have a significant impact, but the latter will be much less predictable than the first.

When gravitation is compared, Earth's would be +/- 978 cm/sec2, while Mars's gravitation is estimated at 371 cm/sec2. 978/371 = 2.64, so the 410 ft x 2.64 = 1081 ft. That would seem a mighty drive for anyone if the two atmospheres were comparable. But they are anything but!

Earth's gravity and Venus's gravity are almost identical, but if we were putting up a fence on Venus, a 410-ft fence might as well be 2 miles away. Atmospheric pressures on Venus are 100 times that of Earth, so driving a ball through that layer of carbon dioxide smog would require a mighty, mighty bat.

Mars's atmospheric pressure is estimated at 0.6% that of Earth's. Again, some quick calculations should yield the lower atmospheric drag on the bat and ball to determine the "atmospheric" adjustment. But it is not so simple; here again we cannot think of this in earthly terms. The extreme thinness of the atmosphere and the generally colder temperatures will produce some very "Mars Only" considerations. This thin atmosphere is easily varied by minor climatic events that would produce far less change in Earth's heavier atmosphere. Martian temperature changes could easily produce sudden gusty winds roaring over 100 miles/hour. As winter approaches and more of the carbon dioxide becomes crystallized at the poles, the already thin atmosphere will become even thinner. Parks near the poles will play far differently than those near the Martian equator. Home runs will be even easier to hit then, unless the ball runs into an unexpected 200 mile/hr blast of wind on its way to the fence!

Good luck commissioner. Your Martian game will add elements never dreamed of back on good ol' Earth!

Classroom Answers