[meteorite-list] 'Scary Storm' on Mars Could Doom Rovers

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 5 Jul 2007 17:41:16 -0700 (PDT)
Message-ID: <200707060041.RAA23435_at_zagami.jpl.nasa.gov>

http://www.space.com/news/070705_dusty_rovers.html

'Scary Storm' on Mars Could Doom Rovers
By Dave Mosher
space.com
05 July 2007

A giant dust storm that now covers nearly the entire southern hemisphere
of Mars could permanently jeopardize the future of the Mars Exploration
Rovers mission, officials told SPACE.com today.

The new and potentially bleak outlook is a stark shift from the
prognosis earlier this week. Michael Malin of
Malin Space Science Systems said in e-mail interview that a smaller,
second dust storm has recently appeared on the Red Planet, further
compounding the threat to the rovers.

The largest dusty squall has reduced direct sunlight to Mars' surface by
nearly 99 percent, an unprecedented threat for the solar-powered robotic
explorers. If the storm keeps up and thickens with even more dust,
officials fear the rovers' batteries may empty and silence the robotic
explorers forever.

"This is a scary storm," said Mark Lemmon, a planetary scientist at
Texas A&M University and member of the rover team. "If it gets any
worse, we'll enter into some uncharted territory. There's been a lot of
discussion about what we're going to do if (the rovers) don't have
enough power to run during the day."

The storm, first reported by SPACE.com, hasn't
yet reached global proportions, but the dust levels are the thickest the
rovers have ever experienced. Lemmon said the conditions rival Mars'
global storm of 2001 and another in 1971.

"This thing has been breaking records the past few days. The sun is 100
times fainter than normal," he said. "We're hoping for a big break in
the storm soon, but that's just a hope."

Double dusty trouble

In exactly two weeks, the larger dust storm ballooned from a small
230,000 square miles (600,000 square km) to its present size at nearly 7
million square miles (18 million square km), Malin explained. In just a
few days, however, its smaller counterpart has emerged as a
3-million-square-mile (7.7-million-square-km) dust bowl. Together, they
cover an area larger than the United States, Canada and Greenland combined.

"These large dust events are not a single storm, but are actually made
up of a number of local and regional-size dust storms," Malin said. By
kicking up enormous amounts of dust, they generate giant dust clouds
that can obscure the planet's surface. Once the dust is lifted, he
noted, the atmosphere warms and can feed the dust-churning events.

The MER team would be more concerned than at present, Lemmon noted, but
early in the storm's genesis, windy conditions swept off
light-blocking layers of dust from Spirit and Opportunity.

Caused by Martian dust devils and
steady wind, the "cleaning events" doubled the rovers' power to around
800 watt-hours last week and boosted hopes of Opportunity's planned
descent into Victoria Crater. As the small storm
gathered fury, however, Opportunity's energy-gathering ability has been
slashed to a dangerous 280 watt-hours-enough power to light only three
90-watt light bulbs.

"The worst-case scenario is that enough dust in the sky decreases solar
energy to the point that we have to shut down too many things to save
power," Lemmon said. "The rovers keep their battery alive by keeping
their electronics alive."

John Callas, project manager for the Mars Exploration Rover (MER)
mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
explained that a dead rover battery could allow cold temperature to maim
Opportunity's electronics.

"It's like leaving your laptop out in an Antarctic winter," Callas said.
"Soldered joints in the electronics can contract due to thermal
contraction. If a rover gets too cold, something essential will fail."
Callas explained the situation is unprecedented, so the team isn't
certain how much more light-blocking dust the rovers-especially
Opportunity-can take.

Fast and furious

Callas said the storm's growth rate was shocking.

"The rovers have weathered weaker storms in the past, which developed
over the course of weeks, but nothing like this. This thing came out of
nowhere," he said. "The dust levels just skyrocketed."

John Wilson, a planetary scientist who studies Mars' atmosphere at the
National Oceanic & Atmospheric Administration in Princeton New Jersey,
says the topography of Mars' southern hemisphere is probably to blame.

"The southern hemisphere, on average, is about 4 km (2.5 miles) higher
than the northern hemisphere, which helps dust storm formation go
global," Wilson said, explaining that Earth experiences a similar
storm-fueling phenomenon near India. "Tibet is high in regards to
mainland India, and so its height helps intensify the Indian monsoon,"
he said, by generating windier conditions at lower elevations.

"Although the storm threatens the rovers, it's giving us a great
opportunity to track another powerful dust storm from start to finish,"
Wilson said. "We get to see where a storm starts and how it grows, then
enter that information into a model to help us predict Martian weather
in the future."

Callas noted that global dust storms spawn
about every three Martian years (about six Earth years), and the last to
occur was about two Martian years ago-so the current storm's potential
to become a global event is on cue. If it does, Callas and his team will
only be able to cross their fingers.

"The reality of the situation is that we're limited as to what we can do
from the ground by cutting power use," Callas said. "If it continues to
worsen and stay that way, it's a survivability issue for Opportunity. If
Mars wants to kill the rovers, it can."
Received on Thu 05 Jul 2007 08:41:16 PM PDT