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NASA Mars Exploration Program
Mars Exploration Program


Comet ISON streaks through a star-filled sky on its way around the Sun.
are giant snowballs in space
made of ice, frozen gases,
rocks, and dust.

Image Credit: NASA/MSFC/Aaron Kingery

Two comets head in toward a young Solar System, with rings of rocky debris and newly formed planets. (Artist's concept)
Click for image information

Image Credit: NASA/JPL-Caltech

About 4 billion years ago
in a newly formed solar system, icy comets
often crashed into a newly formed planet Mars.
Comets likely brought
trillions of pounds
of new material to Mars each year.
Add that up over millions of years
and that's quite a lot of incoming material!
During this ancient time, some
scientists think that comets likely
brought an enormous amount of
to Mars (and Earth!).
That's because comets
contain a lot of
water ice

along with other simple compounds
(e.g., ammonia, methanol, and carbon dioxide).

Image Credit: NASA/JPL-Caltech

Comets may have seeded Mars and Earth
with carbon-based molecules called

- the chemical building blocks of life as we know it.
The nucleus of this comet has dark material that may be organics
Many comets we see today contain
dark, organic material.
When comets impacted ancient Mars, the force
of their impact and resulting shockwaves likely
provided an enormous supply of

(not to mention high temperatures!).

Image Credit: Tim Wetherell - Australian National University

It's possible that these extreme conditions
sparked numerous
chemical reactions

among organic and other compounds,
creating the pre-conditions necessary for life.