Challenge Questions

Challenge Question #1: Martian Baseball
In the six weeks leading up to each live television broadcast, we promised a weekly Challenge Question to get your brain cells firing.

This first one is about baseball on Mars. Some of the PTK veterans may recognize this question from the past, but we couldn't resist with the World Series rapidly approaching. Henceforth, you'll be greeted with only originals. Here now, Challenge Question #1:

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:
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 ofMars. 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, 410ft / 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 further. 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!

ANOTHER 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 that the first.

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

Earth's gravity and Venus' 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' atmospheric pressure is estimated at .005% 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 CO2 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!

Challenge Question #2
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 surface feature elevations 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 breath 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' 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 ! So therefore, it wouldn't seem as impressive to the eye.

Challenge Question #3
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 Mars rotates on its axis. Thus, to an observer on the surface, Phobos appears to "leave the observer behind" and so appears to move from west to east. Thus, from the surface of Mars, the two moons are seen to travel in opposite directions.

NOTE: This a good brain teaser in relative motion. Students and teachers may wish to use models of Mars and its moons to help see the situation better.

Challenge Question #4: Windstorms on Mars

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 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. A listing of the students who submitted answers to this Challenge Question will appear on the LFM Web site shortly.

Challenge Question #5: MS. Stickney
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 featured 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.

Challenge Question #6: Getting to Mars
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' 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 mean 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.

Challenge Question #7:
If geology is the study of Earth (from the Greek geo-earth and logos- knowledge), what should the study of Mars be called?

Areology, of course! "Ares" from the Greek meaning Mars. Remember, Pathfinder will land in Ares Valles, the Valley of Ares!

Challenge Question #8: WHO ARE THEY?
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!

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? Bonus question: Whatever do we mean when we say this feature may make Earth unique compared to the planets...but maybe not "the moons" of our solar system?

Challenge Question #10: 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 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.

BONUS QUESTION:br> If you think about how astronomers measure the height of features on Mars, you'll have a clue to help you answer this question. What do we mean?

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.

Challenge Question #11: BRUSH UP ON YOUR GREEK:
There's a letter in the Greek alphabet that's very important both to launching NASA's current Mars missions and to getting to Mars. What's that letter and explain how it is used.

Both Mars Pathfinder and Mars Global Surveyor were launched aboard Delta II rockets from Cape Canaveral, as seen during LFM program 101. "Delta V" is what rocket scientists (including the Navigation teams who were featured during program 102) 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.

Challenge Question #12: COMPARATIVE ANALYSIS
What five features make Mars most like Earth? And, what five features make Mars most unlike Earth?

ANSWERS: Students have come up with some new points of comparison between Earth and Mars, but these are some of the more obvious and acceptable answers:

- atmosphere: though Mars' is much thinner than Earths
- 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!!!

- 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

Challenge Question #13:
Where and what was the lowest Martian temperature ever recorded?

The temperature was -275 degrees Fahrenheit, recorded during Pathfinder's EDL, the July 4 Entry, Descent and Landing sequence, at 80 km above the surface of Mars.

Challenge Question #14:
NASA's Mars experts are tracking temperature, wind speed and direction. To do that accurately, they place the meteorology mast at the end of one of the solar panels. Why do they do that, rather than closer to the main body of the spacecraft?

Hint: Why do terrestrial weathercasters put their instruments in the middle of open fields?

Answer: Researchers want to maximize their chances of recording measurements unaffected by the warmth of the lander's other instruments and fluctuations in wind speed caused by the flow of the wind over the bulk of the lander.

Challenge Question #15:
There may or may not be a face on Mars, but there's certainly a grin! What is it and where is it?

Hint #1: On Mars you might need Sojourner's camera to see it because there's no mirror for this face to look in.

Hint #2: This is far and away our most impish Challenge Question ever!

As Pete Smith said in one of the early press conferences, the Imager for Mars Pathfinder (IMP for short) has two camera "eyes" and just beneath them a curved line of indentations required by engineering considerations. It was Pete, designer of the camera, who described this as looking like a grin.