[meteorite-list] Hitch Hike To Mars Inside An Asteroid

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Oct 23 14:57:51 2006
Message-ID: <200610231857.LAA12930_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn10358-hitch-hike-to-mars-inside-an-asteroid.html

Hitch hike to Mars inside an asteroid
David Shiga
New Scientist
23 October 2006

Burrowing inside an asteroid whose orbit carries it past both the Earth
and Mars could protect astronauts from radiation on their way to the Red
Planet. The idea is being investigated with funding from NASA.

Outside the protective bubble of the Earth's magnetic field, charged
particles from the Sun and from beyond our solar system in the form of
cosmic rays pose a hazard to astronauts.

Long-term exposure to this space radiation could increase the risk of
astronauts developing cancer and could interfere with their memory and
attention skills (see Future Mars astronauts have radiation on their
minds
<http://www.newscientistspace.com/article/dn10132-future-mars-astronauts-have-radiation-on-their-minds.html>).

Building shielding on Earth to launch with the spacecraft would add a
lot of extra weight to the vehicle and would increase the cost of the
mission as a result. Other ideas, like a lightweight plasma bubble that
could be generated in space are being explored, but have disadvantages
of their own (see Plasma bubble could protect astronauts on Mars trip
<http://www.newscientistspace.com/article/dn9567>).

Now, the NASA Institute for Advanced Concepts (NIAC) in Atlanta,
Georgia, US, is funding a study to see whether asteroids could be used
for radiation shielding. The study is being carried out by Daniella
Della-Giustina, a student at the University of Arizona in Tucson, US.

Protective burrow

A small population of asteroids pass by both the Earth and Mars in their
orbits. So the idea is that a spacecraft containing Mars-bound
astronauts could rendezvous with one of these objects as it goes by the
Earth and travel with it until it nears the Red Planet.

In one version of the idea, the astronauts would actually dig a hole in
the asteroid, put the spacecraft inside and cover it over with material
from the asteroid. Within this protective burrow, the spacecraft would
be shielded from cosmic rays during the six- to 10- month journey to Mars.

In a second version, the spacecraft would not contact the space rock.
Instead, it would hover nearby, and astronauts or robots would visit it
on spacewalks. "You'd have the astronaut actually go to the asteroid and
begin to extract material," Della-Giustina told New Scientist.

The material collected could then be brought back and put into a hollow
shell surrounding the spacecraft. The shell of rocky debris would make a
radiation shield, she says.

The plan has some potential hurdles, but nothing that seems to rule it
out, says Daniel Durda of the Southwest Research Institute in Boulder,
Colorado, US.

Pebbly material

He says it is unlikely that such a rendezvous would significantly alter
the asteroid's orbit but that the possibility should be investigated
further. Orbital changes could potentially divert it from its close
approach to Mars or even put it on a future collision course with the Earth.

Another problem is that the material on the surface of asteroids may not
be that easy to work with, he says. Some asteroids that have been
investigated close up, such as Itokawa, do show rubbly material on their
surfaces, but it is not fine-grained soil like on the Moon, he says.

There could also be a problem with static electricity. Ultraviolet light
from the Sun is expected to cause accumulations of electric charge on
the surface of asteroids, Durda says. This could cause bits of material
to stick to and gum up whatever machinery might be used to work the
surface of the asteroid, he says.

Secondary particles

But if these problems can be overcome, asteroid material has an
advantage because it does not need to be lifted out of a strong
gravitational field like the Earth's, he says. "It would be a wonderful
resource for radiation shielding," he told New Scientist.

Della-Giustina has compiled a list of 40 asteroids with orbits that
cross those of both the Earth and Mars. As part of her study she will
make observations of these objects to see if any are B-type asteroids,
which contain a relatively small proportion of heavy elements.

Heavy elements produce dangerous secondary particles when struck with
cosmic rays, so are not well-suited for radiation shielding.

If further study indicates that using material from asteroids for
radiation shielding is practical, she hopes a robotic mission would be
sent to investigate the best candidate at close range to better
determine its properties.
Received on Mon 23 Oct 2006 02:57:45 PM PDT