successfully in orbit above the planet.
Hurtling through space for the past 10 months, the Maven craft slammed
on the brakes by firing its thrusters.
The 33-minute burn removed sufficient speed to allow the satellite to
be captured by Mars' gravity.
Maven has been sent to study the Red Planet's high atmosphere, to try
to understand the processes that have robbed the world of most of its
air.
Today, the air pressure is so low that free water at the surface would
instantly boil away.
Maven's data will enable scientists to build better models of current
and past climate conditions on Mars.
"Previous spacecraft have made measurements and we've learned a lot
about the upper-atmosphere, but we haven't been able to put the whole
end-to-end picture together," said principal investigator Bruce
Jakosky.
"I'm hoping Maven will be a mission of discovery, that almost
everything we observe will lead us to fundamental new insights about
the Mars environment today and how it has evolved over time," the
University of Colorado, Boulder, researcher added.
Busy time
The American probe's arrival will be followed 48 hours later by
India's first satellite to the Red Planet.
The Mars Orbiter Mission, informally known as Mangalyaan, has slightly
different objectives.
But one important atmospheric study it will try to make is an
observation of methane - a potential indicator of biological activity
on the planet.
"Nasa is really quite interested in cooperating and correlating
data-sets," said Dr Jim Green, Nasa's director of planetary science.
"As both spacecraft get into orbit and the scientists understand their
data, those opportunities will open up."
Monday's big manoeuvre on Maven's engines placed the satellite in a
high, elliptical, 35-hour orbit around the planet.
Confirmation of capture was received on Earth shortly before 0230 GMT
(2230 EDT Sunday; 0330 BST).
In the coming weeks, engineers will then work to bring Maven into a
regular 4.5-hour, operational orbit that takes the probe as close as
150km to Mars but also sends it out to 6,200km.
These first few weeks will also be used to commission and test the
instrument packages on board.
The present-day atmosphere of Mars, composed mostly of carbon dioxide,
is extremely thin, with atmospheric pressure at the surface just 0.6%
of the Earth's surface pressure.
The Martian landscape, though, retains channels that were evidently
cut by abundant, flowing water - proof that the planet had a much
denser atmosphere in the past.
'Deep dip'
Some of the air would certainly have reacted with, and been
incorporated into, minerals at the surface.
But the most likely explanation for its loss is that the solar wind -
the great outflow of energetic particles from the Sun - has simply
eroded it through time.
This has been possible because, unlike Earth, the Red Planet lacks a
protective global magnetic field, which is capable of deflecting the
abrasive assault from our star.
Some of Maven's instruments will concentrate on the Sun's influence,
looking at how much energy it puts into the planet and its atmosphere.
Others instruments will investigate the composition and behaviour of
the atmosphere itself, and this will involve some "deep dip"
manoeuvres that take Maven closer to Mars' surface so it can sample
air molecules directly.
The intention is to measure the rates at which these different
molecules are being lost today, distinguishing between the various
processes responsible.
Scientists will use this information to get some insights into the
history of the Martian climate - from the time billions of years ago
when it was warmer and wetter, and potentially habitable to life, to
the present environment which is cold and desiccated.
Important inputs will come from Nasa's Curiosity rover, which is
studying the bottom of the atmosphere.
Its onboard lab equipment regularly analyses Martian air.
The robot has already used the concentration of argon to show an
enrichment of the heavier form of this element has occurred through
geological history.
It is evidence that lighter argon atoms have been lost preferentially
from the top of the atmosphere.
Comet opportunity
An early demonstration of Maven's capabilities will come in October
when Comet Siding Spring makes a close pass of Mars.
This is likely to dump a lot of dust on the planet.
"If significant amounts of dust hit the upper-atmosphere, we'll see
increases in the temperature... and it will expand," said Prof Jakosky.
"In addition, the water from the comet that hits the upper-atmosphere
will begin to populate it with an extra set of molecules.
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