Solar power SUCKS. Nuclear plutonium batteries in space probes are 1000x
better.

CNN:

The Nasa landers did plenty of science but did not see much of the planet
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* Red Planet 'may not be lifeless'

Nuclear decay-driven machines could gather gases from the atmosphere of
Mars, giving future robotic missions leaps of a kilometre, researchers
say.

A design concept in Proceedings of the Royal Society A outlines an
approach to compress CO2 and liquefy it.

The liquid would then be heated much as in a standard rocket, expanding
violently into a gas to propel exploratory craft great distances.

The authors suggest this is a better strategy to see more of the Red
Planet.

While the Mars rovers Spirit and Opportunity provided far more data than
was initially planned, as vehicles that are powered by the sun and get
around on wheels, they are limited in their overall range of exploration.

For example, the Opportunity rover, which has been on the Martian surface
for nearly seven years, passed the 25-kilometre mark this week.

As a result, researchers have been looking into means of getting farther
with future robotic missions to Mars. Ideas including landers with wings
or lighter-than-atmosphere balloons have been proposed, or even
"inflatable tumbleweeds" that are blown across the landscape.
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“Start Quote

Because you're collecting your propellant from the Martian atmosphere
you're not limited by having to take propellant out from Earth”

End Quote Hugo Williams University of Leicester

However, Hugo Williams and his colleagues at the University of Leicester
- working on the propulsion ideas for a lander project including the
aerospace giant Astrium - argue that a lander that can gather up its own
fuel is best.

At the heart of the idea is a radioisotope-based generator - a few-
kilogram piece of radioactive material that heats up as it regularly
spits out tiny subatomic particles.

"Nuclear batteries" employing the same principle have been in use in
long-term space missions since the Pioneer craft of the early 1970s.

In the proposed hopper design, heat from the decay is gathered and used
to run a compressor, collected the CO2-rich Martian atmosphere into a
tank and compressing it until it turns into a liquid.

Some of the heat is channeled to another block of material that is used
as a storage heater. When a boost is needed the liquid is allowed to
contact the block, quickly turning back into a gas and heating up.

When passed through a standard rocket nozzle, the expanding CO2 gas
provides thrust that can launch a lander and provide a soft landing when
it "hops" to its new locale.

"The advantage is that the radioisotope source is long-lived and not
dependent on solar energy," Dr Williams explained to BBC News.

"You can operate for a long time, and in areas of Mars where the amount
of sunlight is relatively small. Because you're collecting your
propellant from the Martian atmosphere you're not limited by having to
take propellant out from Earth."

The concept design would require a week to gather sufficient propellant
for a hop of about a kilometre, but eventual designs will accommodate the
needs of exploratory missions, pausing less or more time at each landing
site.