[meteorite-list] MAVEN Set For Launch on Atmospheric Research Mission

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 17 Nov 2013 18:17:52 -0800 (PST)
Message-ID: <201311180217.rAI2Hqkn015173_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/atlas/av038/131117preview/

Mars orbiter set for launch on atmospheric research mission
BY STEPHEN CLARK
SPACEFLIGHT NOW
November 17, 2013

The Mars Atmosphere and Volatile Evolution, or MAVEN, mission carries
a suite of instruments built by scientists across the United States to
sample the red planet's upper atmosphere and gauge its composition, dynamics
and response to a stream of radioactive particles from the sun.

Scientists do not know how Mars transformed from a world with lakes, rivers
and potential life into a barren planet without any sign of life today.

"We're trying to understand why the climate changed on Mars - why Mars
appears to have gone from an environment that was habitable, to microorganisms
at least, to one that is the cold, dry, uninhabitable environment we see
today," said Bruce Jakosky, MAVEN's principal investigator from the University
of Colorado at Boulder's Laboratory for Atmospheric and Space Physics.

Data from ongoing Mars missions, including NASA's Curiosity rover, have
convinced scientists Mars once had ample moisture and harbored warmer
temperatures, giving it all the ingredients necessary to support life
at some point in its 4.6-billion-year history.

"We don't just launch missions to Mars one at a time," said John Grunsfeld,
head of NASA's science division. "We have an integrated program of Mars
exploration. We've been following a path of looking for water on Mars,
looking for current water and past water. We've now confirmed that ...
We're transitioning into the search for biosignatures, past evidence that
life could have started on Mars. And we don't have that answer yet. That's
part of the quest trying to answer, are we alone in the universe, in a
broader sense."

Despite an onslaught of missions over the past decade-and-a-half, including
four rovers, a stationary lander, and four orbiters, there is scant evidence
for how and when Mars lost its thick atmosphere, leaving a thin blanket
of gas just above the surface.

Scientists posed that question when developing the proposal for the $671
million MAVEN mission in 2003, Jakosky said.

"One of the big questions has been what happened to the climate? Why did
it change? What we're trying to do is answer that question of where did
the water go? Where did the [carbon dioxide] from the early thick atmosphere
go? There are two places it can go," Jakosky said. "It can go down into
the crust and be locked up there, or it can go up and be lost to space.
We have evidence that both of those happened, but we don't see reservoirs
of [carbon dioxide] in the crust that could explain what happened to the
early thick atmosphere. We're trying to explain the role of loss to space."

Asked if he felt anxious, nervous or excited on the eve of launch, Jakosky
replied: "All of the above."

MAVEN is the first mission dedicated to surveying the Martian upper atmosphere,
and the probe also hosts an Electra radio to join NASA and European orbiters
providing communications relay between Earth and the rovers on the surface.

"By looking at the nature of the upper atmosphere today, we learn about
the processes that control the atmopshere, and we're going to have a good
understanding of what the history of the atmosphere has been," Jakosky
said.

Fitted with eight instruments, MAVEN is set to blast off from Cape Canaveral,
Fla., at 1:28 p.m. EST (1828 GMT) Monday aboard a United Launch Alliance
Atlas 5 rocket.

Powered by a Russian-built RD-180 engine, the Atlas 5 will ascend from
the Florida coastline, break the sound barrier about 78 seconds into flight
and rocket into the upper atmosphere in four minutes before releasing
its kerosene-fueled first stage to fall back into the Atlantic Ocean.

An RL10 engine on the Atlas 5's Centaur upper stage will ignite two times,
first to put MAVEN in a parking orbit around Earth, then to shoot the
5,420-pound spacecraft toward Mars. Deployment of MAVEN is expected about
an hour after launch.

MAVEN is programmed to radio its status to a pair of ground stations in
Australia moments later, and its two wings of power-generating solar panels
should be unfurled within 15 minutes of spacecraft separation, according
to David Mitchell, MAVEN's project manager at NASA's Goddard Space Flight
Center in Maryland.

The solar arrays stretch 37.5 feet tip-to-tip, about the length of a school
bus. Filled with propellant, MAVEN weighs about the same as a fully-loaded
SUV, according to NASA.

The trip to Mars will take 10 months, and MAVEN is due to put itself into
orbit there with a make-or-break 38-minute braking burn scheduled for
Sept. 22, 2014, assuming the launch occurs as planned Monday. "There's
quite an interest in this mission," said Omar Baez, NASA's launch director
for the MAVEN mission. "You wouldn't think so in that it's not as sexy
as the rovers going over the planet, but this is kind of like a weather
satellite for mars, and it's providing relay. It's real science."

Several more engine firings next fall will put MAVEN into its operational
orbit, which will take the probe as close as 93 miles to Mars and as far
as 3,860 miles, completing lap of the planet every four-and-a-half hours.

"Every orbit, we're dipping down below the altitude from which gas is
lost, so we sample that column directly on every orbit," Jakosky said.

The probe has to extend several instrument booms once it arrives at Mars,
allowing MAVEN's sensors to be far enough away from the spacecraft to
avoid interference and collect pristine measurements. One of the deployable
platforms holds three instruments, allowing those sensors to pivot and
point toward Mars while the craft's solar arrays are aimed the sun to
charge its batteries.

By early November 2014, MAVEN should be ready to begin its science campaign,
which will last at least one Earth year. MAVEN's science instruments come
from institutions across the United States and France. Some of the payloads
will track the sun's influence on Mars.

"Mars is responding in various ways, literally bristling with loss processes,"
said Janet Luhmann, MAVEN's deputy principal investigator from the University
of California at Berkeley. "MAVEN is instrumented specifically to be able
to measure what's coming in and what's going out."

Unlike other Mars missions, MAVEN does not carry a camera. As a cost-saving
measure, Jakosky said he decided to limit MAVEN's expenditures to those
focused on its prime science mission.

Other sensors will identify the gases, ions and elements making up the
tenuous outer reaches of the Martian atmosphere.

"This will allow us to estimate over long time periods, on the order of
billions of years ... how long Mars has been exposed to this loss process
and, therefore, how much atmosphere has been removed in this way," Luhmann
said.

One way MAVEN will try to quantify how much of the atmosphere was lost
to space is measuring concentrations of heavy and lighter isotopes of
gases. Scientists think Mars should hold a greater number of heavy isotopes
because lighter atoms would have been easier to strip away with the solar
wind, a stream of charged particles coming from the sun.

"Over billions and billions of years, you leave more of the heavy stuff
in the atmosphere," said Paul Mahaffy, lead scientist for one of MAVEN's
instruments.

"What got me into this were the measurements of isotopes of the noble
gases in the atmosphere," Jakosky said. "The key one that got me excited
about this was the ratio of argon-38 to argon-36 because on Mars, it's
been measured through Martian meteorites and now confirmed with [the Curiosity
rover], that the ratio of argon-38 to argon-36 is about 20-to-30 percent
greater than on Earth, and the only thing that can explain that is loss
to space, so to me that's a direct measurement proving that atmospheric
loss to space was an important process."

Earth's strong magnetic field makes it more resistant to atmospheric decay
from the solar wind, but Mars does not have the global magnetism required
to hold on to air over billions of years.

"We think that escape to space has been responsible for removing a lot
of gas from the atmosphere, and we designed this mission to try to understand
how those processes work, and see if we can measure things that will tell
us how much gas has escaped over time," Jakosky said.

MAVEN will get to Mars just after the peak of the sun's 11-year solar
cycle, so scientists hope to get a front-row seat on how a strong solar
wind impacts the planet's atmosphere.

"What we're really getting at is understanding the history of the climate,
the history of the volatile inventory, and I think the understanding of
the history of the habitability of Mars by microbes," Jakosky said. "I
see it as a geology mission, or an astrobiology mission, because that's
what we're getting at by studying the top of the atmosphere and its interactions
with the sun."
Received on Sun 17 Nov 2013 09:17:52 PM PST