Curiosity Feels A Storm Coming; Nine New Images Of Asteroid 2007 PA8

This nearly global mosaic of observations made by the Mars Reconnaissance Orbiter on Nov. 18, 2012, shows a dust storm in Mars’ southern hemisphere. Yellow arrows outline the area where large clouds of dust are on the move. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS

As spring begins in Mars’ southern hemisphere, seasonal dust storms are already kicking into gear. NASA’s Mars Reconnaissance Orbiter (MRO) has been tracking a significant storm from orbit since last week. Though still more than 800 miles from both the Opportunity and Curiosity rovers, Curiosity’s weather station has already detected changes in the atmosphere including a drop in air pressure and slightly warmer overnight temperatures.

Closeup of an earlier Martian dust storm as it chugs across the planet. Credit: NASA

“This is now a regional dust storm. It has covered a fairly extensive region with its dust haze, and it is in a part of the planet where some regional storms in the past have grown into global dust hazes,” said Rich Zurek, chief Mars scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “For the first time since the Viking missions of the 1970s, we are studying a regional dust storm both from orbit and with a weather station on the surface.”

On Mars as on Earth, the sun rises higher in the sky during spring, heating both air and ground. Temperature differences between the quickly-warming ground and the chilly south polar region drive strong winds which pick up dust and loft it into Mars’ thin atmosphere. There it’s heated by the sun and warms the surrounding air, causing a rise in air temperature. Curiosity has measured a 45-degree Fahrenheit increase in the temperature 16 miles above the Gale Crater landing site.

The global dust storm of 2001 before it started (left) and when it peaked. Photos from the Hubble Space Telescope. Click to enlarge. Credit: NASA / J. Bell

Both rover sites are experiencing elevated dust levels “typical of a hazy summer day in Los Angeles” according to the MRO weather report of the week. Along with winds, warmer air temps also cause water ice clouds across the Martian tropical latitudes to diminish. Scientists are eager to study storms like this one to determine why some remain regional, while others go global. Regional storms from 2001 and 2007 expanded and affected vast areas of the planet.

I remember 2001 in particular. Amateur astronomers looked forward that year to Mars’ close approach to Earth. Just when the planet was at its biggest and best, a regional dust storm went global and veiled all but the largest surface features. This month’s storm might be starting to settle, but only continued observation will tell.

Nine new radar images of the one-mile-wide near-Earth asteroid 2012 PA8 were obtained between Oct. 31 and Nov. 13, 2012, with data collected by NASA’s 230-foot-wide Deep Space Network antenna at Goldstone, Calif. Click to enlarge to appreciate the finer details. Credit: NASA/JPL-Caltech

NASA also just released a new collage of radar pictures of the near-Earth asteroid 2007 PA8 that missed Earth by a comfortable 4 million miles back on Nov. 5. The images are not only crisper that the previous batch of three, they reveal boulders, a decidedly irregular shape, possible craters and a slow rotation.

Detail from Nov. 5 with boulders. Credit: NASA

While the resolution varied according to the asteroid’s distance, it was as fine as 12 feet per pixel (one of those little salt-and-pepper squares in the black and photos above) during closest approach on Nov. 5 and 6.

New radar measurements during the flyby allowed scientists to refine the asteroid’s orbit and predict its motion more than 600 years into the future. The good news? 2007 PA8 isn’t a threat to Earth now or hundreds of years down the road. Its 2012 visit was the closest since 1880 and won’t be bested until 2488, when it zooms 3.6 million miles from Mother Earth.

3 Responses

  1. Sebastien

    Hi Bob, thanks for the pictures from asteroid 2012 PA8. There is something I don’t get, regarding how these pictures are made. I thought the radar in California would sent out radio waves toward the asteroid, and thus illuminating it frontally. Here, the light seems to come from another radio source, placed “above” the asteroid. Do you know why is that?

    1. astrobob

      Excellent question! First, radar image brightness is based on how reflective certain textures/landforms are rather than chemical makeup. Brighter areas are typically rough and bouldery, while dark areas are smooth. That probably doesn’t explain the the appearance of illumination from above. That’s most likely due to the compression of the radio waves from the part of the asteroid rotating toward the Earth. The beam from the radio dish goes out into space, strikes the forward-moving edge of the asteroid and returns compressed (shorter wavelength) and brighter than areas rotating away from Earth. Longer, less energetic waves from the side of the asteroid turning away from Earth give the other side a darker appearance. There may also be other factors involved with which I’m not familiar. I hope this helps.

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