NASA Mars MRO Hi-Rise: Martian Dunes Have Tracks of Dry-Ice Sleds

Several types of downhill flow features have been observed on Mars. 

This image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter is an example of a type called "linear gullies." 

Credit: NASA/JPL-Caltech/Univ. of Arizona

NASA research indicates hunks of frozen carbon dioxide -- dry ice -- may glide down some Martian sand dunes on cushions of gas similar to miniature hovercraft, plowing furrows as they go.

 Researchers deduced this process could explain one enigmatic class of gullies seen on Martian sand dunes by examining images from NASA's Mars Reconnaissance Orbiter (MRO) and performing experiments on sand dunes in Utah and California.

"I have always dreamed of going to Mars," said Serina Diniega, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of a report published online by the journal Icarus.

"Now I dream of snowboarding down a Martian sand dune on a block of dry ice."

The hillside grooves on Mars, called linear gullies, show relatively constant width -- up to a few yards, or meters, across -- with raised banks or levees along the sides.

Unlike gullies caused by water flows on Earth and possibly on Mars, they do not have aprons of debris at the downhill end of the gully.

Instead, many have pits at the downhill end. "In debris flows, you have water carrying sediment downhill, and the material eroded from the top is carried to the bottom and deposited as a fan-shaped apron," said Diniega.

"In the linear gullies, you're not transporting material. You're carving out a groove, pushing material to the sides."

Images from MRO's High Resolution Imaging Science Experiment (HiRISE) camera show sand dunes with linear gullies covered by carbon-dioxide frost during the Martian winter.

The location of the linear gullies is on dunes that spend the Martian winter covered by carbon-dioxide frost.

By comparing before-and-after images from different seasons, researchers determined that the grooves are formed during early spring.

Some images have even caught bright objects in the gullies. Scientists theorize the bright objects are pieces of dry ice that have broken away from points higher on the slope.

According to the new hypothesis, the pits could result from the blocks of dry ice completely sublimating away into carbon-dioxide gas after they have stopped traveling.

"Linear gullies don't look like gullies on Earth or other gullies on Mars, and this process wouldn't happen on Earth," said Diniega.

"You don't get blocks of dry ice on Earth unless you go buy them." That is exactly what report co-author Candice Hansen, of the Planetary Science Institute in Tucson, Ariz., did.

Hansen has studied other effects of seasonal carbon-dioxide ice on Mars, such as spider-shaped features that result from explosive release of carbon-dioxide gas trapped beneath a sheet of dry ice as the underside of the sheet thaws in spring.

She suspected a role for dry ice in forming linear gullies, so she bought some slabs of dry ice at a supermarket and slid them down sand dunes.

That day and in several later experiments, gaseous carbon dioxide from the thawing ice maintained a lubricating layer under the slab and also pushed sand aside into small levees as the slabs glided down even low-angle slopes.

The outdoor tests did not simulate Martian temperature and pressure, but calculations indicate the dry ice would act similarly in early Martian spring where the linear gullies form.

Although water ice, too, can sublimate directly to gas under some Martian conditions, it would stay frozen at the temperatures at which these gullies form, the researchers calculate.

"MRO is showing that Mars is a very active planet," Hansen said. "Some of the processes we see on Mars are like processes on Earth, but this one is in the category of uniquely Martian."

Hansen also noted the process could be unique to the linear gullies described on Martian sand dunes.

"There are a variety of different types of features on Mars that sometimes get lumped together as 'gullies,' but they are formed by different processes," she said.

"Just because this dry-ice hypothesis looks like a good explanation for one type doesn't mean it applies to others."

To see images of the linear gullies and obtain more information about MRO, visit: http://www.nasa.gov/mro

For more about HiRISE, visit: http://hirise.lpl.arizona.edu .

NASA Mars Rover Curiosity: Making tracks and Exercising it's robotic arm

NASA's Curiosity rover is having a few days break from travelling to give its arm a work out.

The rover, which has so far driven 358 feet (109 metres) from its landing site, is making its way across Gale Crater.

Having covered about one fourth of the distance to Glenelg, which is 400 metres for the rover's landing site, Curiosity paused on flat ground and extended its 7 foot (2.1 metre) arm which operates a number of Curiosity's tools.

Michael Watkins, the mission manager, explained: "We knew at some point we were going to need to stop and take a week or so for these characterisation activities. For these checkouts, we need to turn to a particular angle in relation to the sun and on flat ground. We could see before the latest drive that this looked like a perfect spot to start these activities."

We're still learning how to use the rover. It's such a complex machine -- the learning curve is steep
Joy Crisp, JPL

"These activities are important to get a better understanding for how the arm functions after the long cruise to Mars and in the different temperature and gravity of Mars, compared to earlier testing on Earth," said Daniel Limonadi.

NASA (ATREX) Launches: Anomalous Transport Rocket Experiment

The ATREX mission will launch 5 Sounding rockets in 5 minutes to gather information to better understand the process responsible for the Earth's high-altitude jet stream.

This map shows the projected area in which the chemical tracers released from the rockets may be visible to the public. Credit: NASA/Wallops

For the 5 Rocket launches to go ahead, clear skies are required at three special camera sites located along the mid-Atlantic coast in Virginia, North Carolina and New Jersey.

The visible tracers may be observed for up to 20 minutes by residents in the mid-Atlantic region, and along the east coast of the United States from parts of New Jersey to South Carolina.

Launch Viewing at Wallops
The launch window each night will vary but will open no earlier than 11 p.m. EST and close no later than 6:30 a.m. The NASA Visitor Center at Wallops will be open at least one hour before the opening of the daily launch window for viewing the mission by the public. Call 757-824-2298 to confirm opening time.

› Launch Sequence PDF

Web Cast
The ATREX mission will be web cast beginning 2 hours before the opening of the launch window. Visit http://sites.wff.nasa.gov/webcast.

Mariners/Boaters
Information for mariners on areas to avoid on the Atlantic Ocean off the coast of Wallops Island during launch operations. Visit: http://www.nasa.gov/centers/wallops/home/marine.html.

ESA Proba-2 Tracks Sun Surging Into Space

Proba-2 is an experimental ESA micro-satellite carrying four solar physics and space weather instruments and a total of 17 new technology payloads.

Proba-2 is a small but innovative member of ESA's spacecraft fleet, crammed with experimental technologies. In its first eight months of life it has already returned more than 90 000 images of the Sun.

Less than a cubic metre in volume, Proba-2 carries a new generation of miniaturised science instruments, focused on the Sun and space weather, as well as 17 state-of-the-art technology payloads.

Launched on 2 November 2009, Proba-2 began routine operations in February. A workshop at ESA's ESTEC research and technology centre in the Netherlands on 22 June highlighted the microsatellite's initial achievements.

"We're getting very good results," remarked John Jorgensen of Technical University of Denmark, which contributed the mission's Micro Advanced Stellar Compass, a miniaturised startracker.

"This kind of platform works very well to provide in-flight demonstration of new technologies."

Four-legged tracks in mud cause paleontologists re-think

Muddy tracks left 397 million years ago may reset the age when the first four-legged animals crawled onto land.

In the Nature journal study, reported Wednesday and led by Grzegorz Niedz´wiedzki of Poland's Warsaw University, a European team reports "numerous" tracks from the Zachelmie mountain quarry that reveal the era when clumsy-limbed fishes forsook the seas to live on land.

The tracks show that four-legged creatures, one of them more than 8 feet long, probably originated in lagoons, not swamps, as suggested by past fossil finds.

A beach "provides a ready food source of stranded marine animals," the study's authors say. That would have allowed marine

ancestors of four-legged creatures to evolve "terrestrial competence" while dining on "a new and essentially untouched resource."

The trackway discovery "is undoubtedly one of the most extraordinary and unexpected finds in paleontology for decades, perhaps a century," says paleontologist John Long of the Natural History Museum of Los Angeles County.

Until the discovery, paleontologists thought the evolutionary transition from fishes to land animals was tightly nailed down to fossils dated about 379 million years old, he says.

The tracks not only push back the age of the first four-legged animals by a "whopping 18 million years," he says, but also "show that quite advanced kinds of tetrapods (four-limbed creatures), with incipient wrist joints, had already appeared by this much earlier stage of animal evolution."

The tracks "lob a grenade" into fossil studies of the earliest land creatures, Philippe Janvier and Gael Clement of the Muséum National d'Histoire Naturelle in Paris say in a commentary accompanying the study.

Paleontologists had considered fish-like creatures such as "Tiktaalik," a discovery that made headlines in 2006, as the likely earliest land animals. Instead, the trackways suggest Tiktaalik was a relic species still adapting to land long after other species had made the transition.

Not so fast, Tiktaalik's discoverers say. "Trace fossils such as these presumed vertebrate tracks and trackways, however, are a notoriously difficult class of evidence to interpret with full confidence," says Ted Daeschler of the Academy of Natural Sciences in Philadelphia by e-mail. "With all respect to the scientists involved in this study, there may be other explanations for these suggestive tracks."

The study authors acknowledge they have only fossil tracks, not bones, from their four-legged creature, which perhaps resembled an oversized salamander. Based on its gait, the critter floated in the tide while making tracks. The authors recommend from their finding that other paleontologists look for fossils of four-legged creatures as far back as 420 million years ago.