1) Could Mars have a third moon that we don't know about? If not, why not?
Sure, Mars could have several other moons. They would have to be much
smaller than the two we know about, though, to have escaped our notice
so far. They would likely be captured asteroids. Many factors could make
them hard to see. If they are very dark objects, as the two known moons
are, it would be like looking for a piece of coal in the dark. If they
have highly inclined orbits, passing over the high latitudes and poles
instead of the equator, we would never see them pass between us and
Mars. Also, if they orbited at great distances, their gravity would not
be easily detected by the spacecraft in orbit around Mars. The point is
that there could be one, lots, or none. We can put limits on what could
be out there based on what we haven't seen, but we can never rule out
all of the possibilities.
2) I believe there is a compact disk aboard the rovers bearing the names of
people. Is it on Spirit or Opportunity?
There are two copies of a DVD with the names of almost four million Mars
enthusiasts, one on each of the rovers. For more information on these
DVDs,
visit
the website.
3) Does Mars have an effect on Earth when its orbit brings it closest to
the Earth? If so, what is this effect?
Mars always has an effect on Earth; it's just very, very, very, very
small. There is a gravitational force between any two objects that
depends on their mass and the distance between them. Although Earth and
Mars are VERY massive, compared to you and me, they are also VERY far
apart, even at closest approach. The force between two objects drops
rapidly as you move them farther apart. Even when Mars is closest to
Earth, the force it exerts on us is over 2000 times smaller than the
force of our Moon. When Mars and Earth are at their farthest distance
apart, this effect drops to over 100,000 times weaker than the force of
the Moon! The result of this force from Mars is teeny tiny changes in
our orbit around the Sun which are much too small for us to notice.
4) What is the name of the asteroid that travels within the orbit of Mars?
There are several asteroids that have orbits that cross the orbits of
the inner planets. They are given different class names depending on
where their orbits are with respect to Earth. Those with orbits between
Earth's orbit and the asteroid belt, which cross Mars' orbit, are called
Amor asteroids. A famous Amor asteroid is Eros, which was visited by the
NEAR spacecraft. Those that cross Earth's orbit are called Apollo
asteroids, and those inside of Earth's orbit are called Aten asteroids.
5) What subjects do you have to take at school to become a planetary
scientist?
In high school, I recommend taking as many advanced math and science
courses as are offered, as well as classes in the arts since these will
build your creativity skills. In college, you have many options. People
approach planetary science from many different fields. You could major
in astronomy, physics, geology/geophysics, meteorology, or engineering
(if you're interested in building and designing spacecraft). Whichever
of these fields you chose to concentrate in, I would still recommend
taking a few classes in some of the other fields. My field of choice is
astronomy, but I have taken classes in both meteorology and geology. As
was said in the article, though, classes other than math and science are
important, too. Learning a foreign language is useful since planetary
exploration is such an international venture. Also, as a scientist you
will spend a great deal of time writing papers and giving presentations
and lectures. One course I found very helpful, and enjoyable, was a
Shakespeare class, in which I had to write several essays and research
papers and perform in front of groups.
6) Why does the northern hemisphere of Mars look so different from the
southern hemisphere?
That is an excellent question. The answer is: we don't know. This is one
of the great mysteries of Mars' geologic history. One theory is that
heat flow through the mantle was very different between the northern and
southern hemispheres early in Mars' history, and so the crusts formed
under very different conditions. Another theory is that the northern
lowlands are an ancient ocean basin and were once completely covered in
water. This is just the type of question we hope to come closer to
answering with exploration missions like MER.
7) I am doing a project about Mars. What are some really interesting
things that I should include?
There is a great deal of current data that suggest the current presence
of water on Mars. Some examples are the gulleys on crater walls,
measurements of hydrogen that indicate subsurface water ice, and
features that look similar to active rock glaciers (ice glaciers
containing a significant amount of rock). A second hot topic is how dust
and wind interact in events such as giant dust devils and dust storms
that can grow to engulf the entire planet. A third topic is the
discovery of hematite, an iron-based mineral often formed in water, on
Mars. It is only found in three very small spots, and the Meridiani
Planum landing site for Opportunity is inside the largest of these.
8) How far can the rovers travel on Mars in 90 days?
The rovers are designed to travel up to 100 meters in one sol (martian
day). However, we won't be driving them every sol. We'll spend many sols
in one spot studying rocks and soil that can be reached by the
Instrument Deployment Device, or IDD (the arm). In the 90 sols that we
expect the rovers to operate on Mars, it is expected that each rover
will travel at least 600 meters, and it is hoped that they will cover
about 1000 meters, or 1 kilometer (a little less than two-thirds of a
mile).
9) How did you get on the Athena science team?
Steve Squyres, the Principal Investigator of the Athena Science Team, is
a Professor of Astronomy at Cornell University. When I applied to
graduate school at Cornell, I indicated in my application essay that I
was very interested in planetary exploration missions. When Dr. Squyres
called to inform me that I had been accepted at Cornell, I asked him
what research and work opportunities there were for me at Cornell.
Obviously familiar with my application, he immediately suggested working
with him on MER. After taking a few seconds to compose myself (after
all, my life-long dream had just come true), I said that would
definitely be something I'd be interested in. That sealed my decision to
attend Cornell, and four months later I was at my first Athena Team
Meeting.
10) Why do the polar ice caps on Mars grow larger and smaller?
Mars' axis of rotation is tilted at almost the same angle as Earth's
with respect to the plane of its orbit (Earth is tilted 23.5 degrees,
Mars is tilted 24 degrees). This means that
Mars has seasons similar to the
seasons here on Earth. When it is summer, the warmer temperatures cause
the polar cap to shrink as the water and carbon dioxide ice sublimate
(transform directly from a solid state into a gas state, without first
melting into a liquid state and then boiling off into the gas state).
During the winter, the colder temperatures cause these vapors to then
re-solidify back onto the caps, a process called deposition (like snow
or frost). Like on Earth, when it is summer in the northern hemisphere
and the northern polar cap is shrinking, it is winter in the southern
hemisphere and the southern polar cap is growing, and vise versa.
11) Will the orbiters around Mars be able to see the rovers?
No, the cameras we currently have in orbit do not have high enough
resolution (image sharpness) to see the rovers. Digital cameras produce
images made up of thousands and thousands of pixels, each a square with
a single color and shade. You can see the individual pixels by taking an
image on a computer and using an imaging program to zoom in on the image
until you can see these squares. The resolution of the camera is then
determined by how big its pixel is in the picture. The best camera
currently in orbit produces images with pixels that are about 1.5 meters
(about 4.5 feet) square. The rovers are only slightly larger than this,
so unless the color and shade of the rover deck is completely unlike
anything else in the area, those two or three pixels would not be enough
to identify it. The next orbiter, called the
Mars
Reconnaissance Orbiter,
will carry a camera that will be able to take pictures with 0.25 meter
square pixels (about the size of one of the wheels), so this camera will
have the capability to see the rovers.
