Explanation:
You're rolling across Mars when you unexpectedly uncover some unusually light soil.
You stop. You turn. You return to inspect the soil and find out it is almost purely
silica -- the main ingredient in
quartz and
glass.
Such soil has never been found on
Mars before. What created this soil?
Since you are the robotic
rover Spirit currently rolling across Mars,
you send the images and data back to
Earth for analysis.
Your scientist friends from the blue water planet say that such soil on Earth is usually created by either volcanic steam or a
hot spring.
The second hypothesis in particular indicates, once again, a
wet past for part of Mars,
as possibly hot water saturated with silica deposited the white soil.
Intriguingly, on Earth, living
microbes
typically flourish under either condition.
Pictured above, the uncovered light soil is
visible on the right.
APOD presents: Astronomy Pictures of the Year for 2007
