Astronomy Now Online

Top Stories

Powerful nearby supernova caught 10 years later

...astronomers have finally identified one of the nearest supernovae of the last 25 years, over a decade after it exploded...

read more

Hibernating magnetar springs to life

...a mysterious celestial object that emitted 40 visible light flashes before disappearing again could be a missing link in the family of neutron stars...

read more

A smart look at the peak of eternal light three-dimensional images taken by SMART-1's AMIE camera show the ‘peak of eternal light’ in new light...

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

Phoenix sees falling snow

Posted: September 30, 2008

Phoenix’s laser instrument has sensed snow falling from Martian clouds, while soil experiments have strengthened the case for past interactions between minerals and liquid water, mimicking conditions on the Earth.

"Nothing like this view has ever been seen on Mars," says Jim Whiteway, lead scientist for the Canadian-supplied Meteorological Station on Phoenix. "We'll be looking for signs that the snow may even reach the ground."

So far, the snow has been detected to fall from clouds at an altitude of four kilometres, although it vapourised before reaching the ground.

This sequence combines 32 images of clouds moving eastward across the horizon over a period of around half an hour. The clouds contain water-ice particles, just like cirrus clouds on Earth. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University

Surface experiments have provided clues for the presence of calcium carbonate, the main composition of chalk, and particles that could be clay, materials that on Earth only form in the presence of liquid water. The evidence came from experiments conducted by both the Thermal and Evolved Gas Analyser (TEGA) and the wet chemistry laboratory of the Microscopy, Electrochemistry and Conductivity Analyser (MECA).

"We have found carbonate," says William Boynton of the University of Arizona, lead scientist for the TEGA. "This points toward episodes of interaction with water in the past."

TEGA’s evidence for calcium carbonate came from the release of carbon dioxide gas at a temperature known to decompose the substance. The MECA evidence came from a buffering effect characteristic of calcium carbonate assessed in wet chemistry analysis of the soil. The measured concentration of calcium was exactly what would be expected for a solution buffered by calcium carbonate.

Both instruments also suggest the presence of a clay-like substance. "We are seeing smooth-surfaced, platy particles with the atomic-force microscope, not inconsistent with the appearance of clay particles," says Michael Hecht, MECA lead scientist at NASA's Jet Propulsion Laboratory.

"We are still collecting data and have lots of analysis ahead, but we are making good progress on the big questions we set out for ourselves," says Phoenix Principal Investigator Peter Smith.

The Phoenix mission, originally planned for three months, is now in its fifth month, but faces a decline in solar energy from permanent sunshine at the start of the mission to currently over four hours of darkness each night. Mission scientists predict that there will not be enough power to operate the robotic arm after the end of October, and all operations will have ceased by the end of the year.

Related Stories

Sep 29 Phoenix peeks under a rock read more

Sep 12 Dust devils pay visit to Phoenix read more

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