NASA’s Mars rover Curiosity snapped this self-portrait on June 15, 2018 at Gale Crater during a growing dust storm. Since then, the dust storm has engulfed all of Mars.
On Mars, the sky is dust.
A massive dust storm on Mars that covered one-fourth of planet just a week ago has grown into a global weather event, NASA officials said Wednesday (June 20).
The dust storm has knocked NASA's Opportunity rover offline for want of sunlight. The agency's nuclear-powered Curiosity, meanwhile, is snapping photos of the ever-darkening Martian sky. The two rovers are on opposite sides of Mars.
"The Martian dust storm has grown in size and is now officially a 'planet-encircling' (or 'global') dust event," NASA officials said in a statement. [The Mars Dust Storm of 2018 Explained]
The last dust storm on Mars to go global occurred in 2007, five years before the Curiosity rover landed at its Gale Crater site, according officials with NASA's Jet Propulsion Laboratory in Pasadena, California. The Opportunity rover has been exploring the plains of Meridiani Planum on the opposite side of Mars since 2004. During that 2007 Martian dust storm, NASA also lost contact with Opportunity for days due to low power levels from the lack of sunlight.
NASA lost contact with Opportunity last week when it missed a check-in call on June 12. NASA engineers think the rover is in a low-power mode, waking up only periodically to check if its batteries have recharged enough to phone home. All science operations by the rover are suspended while it waits out the storm.
The Martian dust storm was first detected May 30 by NASA's Mars Reconnaissance Orbiter. Once it was clear the storm would impact Opportunity, the rover was ordered into a sort of survival mode. A series of photos by Opportunity before it went silent show the Martian sky darkening until the sun itself disappears.
Scientists measure the amount of sunlight-blocking haze in the Martian atmosphere as "tau," with the current tau at Curiosity's Gale Crater site reaching above 8.0, JPL officials said the NASA statement. The last tau for Opportunity's site was over 11. The atmosphere is so thick with dust, "accurate measurements are no longer possible for Mars' oldest active rover."
In a press conference last week, NASA officials said they expect Opportunity will survive the dust storm. Without a steady supply of sunlight, the biggest risk for Opportunity would be freezing in the Martian cold. But it's almost Martian summer at Opportunity's location, and temperatures are not expected to dip below the danger level, NASA officials have said.
That means Opportunity's handlers can only wait until the sky clears enough for the rover's batteries to recharge, allowing it to power up its radio to phone home.
In the meantime, NASA scientists are maintaining a full-court press the Martian dust storm. In addition to Curiosity's weather observations on the surface, NASA has several other spacecraft tracking the storm from orbit: the Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN orbiter studying the Martian atmosphere. The European Space Agency also has two spacecraft in orbit (Mars Express and the ExoMars Trace Gas Orbiter). India's Mars Orbiter Mission spacecraft is also in orbit.
A key question for scientists is why some dust storms on Mars become planet-enshrouding events and last months, while others fade away in a week.
"We don’t have any good idea," Scott Guzewich, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said in the statement. Guzewich is leading the Curiosity rover's dust storm work.
New photos from Curiosity show a wall of haze over Gale Crater that is up to eight times thicker than normal for this time on Mars, NASA officials said. One photo also shows a curious lack of shadows. That's because the entire sky on Mars is red and illuminating the rocks from all sides, NASA officials explained.
While the dust storm won't affect Curiosity's power levels, the low-light conditions are forcing the rover to take longer exposures when it snaps photographs, NASA officials said. When Curiosity is not taking pictures, the rover rotates its mast-mounted Mastcam camera to face the ground to protect it from blowing dust, they added.
You can get updates about the dust storm, and Opportunity's status, at NASA's Mars Storm Watch page.