Updated at 3:00 p.m. ET
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. Further compounding the threat to the rovers, a second large dust storm has recently appeared on the Red Planet.
The first and largest dusty squall has reduced direct
sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for
the solar-powered rovers. 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 230,000 square miles (600,000 square km) to its present size at nearly 7 million square miles (18 million square km), said Michael Malin of Malin Space Science Systems in e-mail interview. 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 clouds that obscure the planet's surface. Once the dust is lifted, he noted, the atmosphere warms and can feed the surface-blocking cycle.
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 each day--only enough to light one 60-watt bulb for less than 5 hours.
"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."
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