Astronomy Now Online

Top Stories

Eta Carinae’s eruptions a multi-stage process

...the outbursts of Eta Carinae, could be driven by an entirely new type of stellar explosion that is fainter than a typical supernova...

read more

Naked-eye gamma-ray burst aimed straight
for Earth

...six months ago the brightest gamma-ray burst ever seen from Earth was picked up by the SWIFT telescope, giving astronomers the most detailed portrait yet of a stellar explosion...

read more

Episodic not catastrophic flooding on Mars simulations suggest that the massive valley networks that define the surface of Mars could have been carved out by recurrent flooding rather than a short-lived catastrophic event...

read more

Spaceflight Now +

Subscribe to Spaceflight Now Plus for access to our extensive video collections!
How do I sign up?
Video archive

STS-120 day 2 highlights

Flight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.


STS-120 day 1 highlights

The highlights from shuttle Discovery's launch day are packaged into this movie.


STS-118: Highlights

The STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.

 Full presentation
 Mission film

STS-120: Rollout to pad

Space shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.


Dawn leaves Earth

NASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.

 Full coverage

Dawn: Launch preview

These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.

 Launch | Science

Become a subscriber
More video

Dust devils pay visit

to Phoenix

Posted: September 12, 2008

After three months of performing experiments in the north polar regions of Mars, NASA's Phoenix Lander has finally seen dust devils, and sensed a dip in air pressure as one passed nearby.

"We expected dust devils, but we are not sure how frequently," says Phoenix Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory. "It could be they are rare and Phoenix got lucky. We'll keep looking for dust devils at the Phoenix site to see if they are common or not."

At least six different dust devils, ranging in diameter from about two metres to five metres, appear in the images captured this week, much smaller than dust devils that NASA's Mars Exploration Rover Spirit has photographed closer to the equator.

Click for animation. The Surface Stereo Imager caught this dust devil in action on 9 September. It was about 1 km away from the Lander when the first frame was taken, ,moving to about 1.7 km away two and a half minutes later. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

"It was a surprise to have a dust devil so visible that it stood with just the normal processing we do," says Mark Lemmon, lead scientist for the stereo camera that captured the dust devils in action. "Once we saw a couple that way, we did some additional processing and found there are dust devils in 12 of the images. It will be very interesting to watch over the next days and weeks to see if there are lots of dust devils or if this was an isolated event."

As well as performing science experiments within the onboard laboratory, Phoenix also monitors the daily air pressure, and on the same day the camera saw dust devils, the pressure meter recorded a sharper dip than ever before seen. Phoenix also recorded wind speeds of at least five metres per second.

"Throughout the mission, we have been detecting vortex structures that lower the pressure for 20 to 30 seconds during the middle part of the day," says Peter Taylor of York University, Toronto, Canada, a member of the Phoenix science team.  "In the last few weeks, we've seen the intensity increasing, and now these vortices appear to have become strong enough to pick up dust."

Phoenix scientists believe that the whirlwinds are getting stronger as the difference in day and nighttime temperatures increases. While daytime highs at the Phoenix site are still about minus 30 Celsius, the nighttime lows have been dropping steadily as summer in the northern hemisphere draws to a close, getting close to minus 90 Celsius.

The decline in daylight hours means that the project scientists must hurry to squeeze every last ounce of science out of the mission before Phoenix is unable to produce the electricity required to dig and perform experiments, which it does via its solar panels. With that in mind, a sample of icy soil from the Snow White trench has been selected for the final cell in the wet chemistry laboratory, and plans are being made to fill the remaining four of eight single-use ovens in the Thermal Evolved and Gas Analyser, without waiting for analysis of each sample to be completed before delivering the next.

"Now that the sun is not constantly above the horizon at our landing site we are generating less power every sol," says Phoenix Project Manager Barry Goldstein. "When we landed in late May, and through much of our mission, we generated about 3,500 watt-hours every sol.  We are currently at about 2,500 watt-hours, and sinking daily.”

Related Stories

Sep 05 Phoenix's vapour quandary read more

Aug 26 Phoenix digs into extended mission... read more

Aug 06 Martian salts analysed for habitability... read more

Aug 01 Phoenix tastes water on Mars read more

Jul   29 Sticky situation for Phoenix read more

Jul   22 Phoenix in 24-hour monitoring assignment read more

Jul   17 Phoenix rasps frozen layer... read more

Jul   11 First success with Phoenix soil probe... read more

Jul   10 Phoenix struggling with icy payload read more

Jul   03 Next Phoenix bake could be last read more

Jun  30 Phoenix soil could support life read more

Jun  23 Frozen water confirmed on Mars read more

Jun  19 Bright chunks must have been ice read more

Jun  17 First results from Phoenix bakery read more

Jun  12 An oven full of sand read more

Jun  10 Clumpy Martian soil challenges Phoenix read more

Jun  06 Closest view ever of Mars sand read more

Jun  03 Phoenix scoops up Martian soil read more

Jun  02 Phoenix sees possible ice read more

May 30 Phoenix flexes robotic arm read more

May 28 HiRISE captures Phoenix descent read more

May 26 Spectacular new colour view of Mars read more

May 23 Phoenix prepares for Mars landing read more