Transcript of the chat held on March 4 with
Dr. Bell, planetary scientist from Cornell University
Dr. Bell holds a Ph.D.in Planetary Geosciences from the University
of Hawaii at Manoa. He is a Research Associate at Cornell University, Department
of Astronomy, Center for Radiophysics and Space Research and Visiting Astronomer,
NASA Infrared Telescope Facility for NASA Near Earth Asteroid Rendezvous
Question : Ok. Jim : first question.
What should we start thinking about in order to choose a good landing site
for our mission?
Answer : A good first question!
You need to think about several issues:
(1) What kind of science or exploration do you want to do?
(2) Where CAN you land? (are there engineering/technical limits?)
(3) Can you be 100% sure that you can land there and return safely?
Question : What about the chaotic
terrain in the S hemisphere?
Answer : Yes! The southern hemisphere
is the oldest terrain, and there are several good choices for places to
Possibly better than chaotic terrain would be ancient lakes, like Gusev
crater near 15 deg. S, 185 deg. W. Most scientists believe that Gusev was
once filled with water... and who knows what else!
OK; let's start with goal #5 because that addresses science.
IF you want to find life on Mars, then you want to look in some very specific
places. I assume that many of you are familiar with last year's famous
"Mars meteorite" story... ?
Well, the upshot of the Mars meteorite story is that it comes from a very
old region of Mars. You mentioned floods: well, evidence for water on the
surface also occurs primarily in the oldest regions. All this leads one
to conclude that Mars was very different long ago...
So while it would be VERY cool to land on the top of Olympus Mons or in
the deepest part of Valles Marineris, we know that these are relatively
young places. If the goal is searching for past (or present!) Mars life,
then the places to go are probably the oldest places, where evidence for
life may be preserved as fossils from a time when Mars was warmer and wetter
than it is today...
Question : Wouldn't it be too risky
to land on Crater Lake (too small a target for a lander)?
Answer : Landing accuracy is constantly
improving for the robotic missions. But just look at Apollo 17 as an example:
skilled astronauts and an excellent spacecraft allowed them to plunk down
in a very small valley between two huge mountain ranges on the Moon. Gusev
is something like 150 km
across, so maybe there's plenty of room for a skilled pilot to land there...
Question : What about choosing a
site that can enable us to explore both ancient and 'new' terrain?
Answer : Ancient and new terrain in
the same area is a tough order. But there are rregions along the boundary
between the southern highlands and the northern lowlands that might work.
Another approach might be to give your landed crew some mobility of hundreds
with a Marscar of some type, or a balloon, or a plane, or make the lander
capable of taking off and landing again somewhere else on the planet...?
Question : What about exploring
the polar ice caps? The best record of the Martian climatic evolution could
be found there?
Answer : Polar ice caps...
Sure, there is a great record of Mars climate evolution there, but hang
on: You said your goal was finding Martian life.
You have to be careful that you stick to your goals, otherwise you are
subject to what the U.S. military calls "mission creep" as you
wander farther and farther away from what you had
The poles are great places geologically and climatically, but at -120 C
they are not very good places for life...
Question : Our goals are temporary,
and we are in the process of discussing them
Answer : Aha.... I see.
OK, well then go back to my first few points: Can you GET to the poles?
It takes a lot of rocket fuel to get to high latitudes, and you'll have
to carry that fuel with you, which means a heavier launch, which means
a bigger rocket, which means more money, .... etc etc. Everything is inter-related
in the real world of space travel...
Question : Are there any technical
limitations which should be considered during the selection of a landing
Answer : Technical limitations that
come to mind quickly:
(1) accuracy (you mentioned this earlier): can an astronaut pilot the spacecraft
to where you want to go?
(2) fuel supply: it takes more fuel to go farther from the equatorial region
(because that's the plane of your incoming orbit). Also, if you want to
use the atmosphere to help slow you down (aerobraking: it saves a LOT of
fuel), then you can't land in high elevation places because there's much
less atmosphere there.
(3) communication: Earth is not always visible from everywhere on the surface,
so if you want direct communication to Earth, you might be limited. Otherwise,
you might need an orbital relay satellite (more money, more complexity,
I'm sure there are others...
Question : While we
don't think plate tectonics is presently occuring on Mars, do you think
it was occuring earlier in the formation of the planet? I have read arguments
on both side of this issue.
Answer : As you say, the issue of plate
tectonics is very controversial. My opinion, based on the scientific literature,
is that Mars never had plate tectonics, even early on. When we look at
the ancient cratered regions in the southern hemisphere, we see almost
all the way back to when the planet was formed. There is little convincing
evidence for plate tectonic landforms in these oldest preserved parts of
Question : Is diverting an asteroid
into Mars really feasible as we have been reading about in futuristic articles?
Answer : Diverting asteroids is not
feasible given our current level of technology because (a) we don't know
enough about asteroids (instead of diverting one we could blow it into
a zillion pieces!), and (b) it's not clear that there are enough explosives,
nuclear or otherwise, on the planet to do the job. Plus you open up a whole
can of worms on the nuclear issue. If we have this giant stockpile (again)
for supposedly peaceful purposes, who's to say that some tyrant or terrorists
won't take it over...
Question : Have you read The Case
For Mars? How valid is the book from your perspective?
Answer : The Case for Mars is a very
ambitous and enthusiastic book.
In today's world, unfortunately, it really is science fiction rather than
science fact, because governments just don't have the money needed to do
a human Mars mission.
However, the idea is sound, and it's only a matter of time before something
like it takes off. Maybe 10 years? 20??
We would like to thank Dr.Bell once more for his generosity in helping
us with this chat. Thanks also to the schools that joined in.