RSSAll Entries Tagged With: "Mars Reconnaissance Orbiter"

Red Planet goes with the flow

Dark flows on Mars

Dark streaks that come and go on some Martian slopes, could be evidence for flows of salty water.

  • Dark, narrow features seen on Martian slopes
  • They come and go with the seasons
  • Could be caused by flows of salty water

DARK, FINGER-LIKE FEATURES that appear and extend down some Martian slopes during the warmest months of the Mars year may show activity of salty water on Mars. They fade in winter, then recur the next spring.

Repeated observations by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter have tracked seasonal changes in these recurring features on several steep slopes in middle latitudes of Mars’ southern hemisphere.

Some aspects of the observations still puzzle researchers.

“The best explanation we have for these observations so far is flow of briny water, although this study does not prove that,” said Alfred McEwen of the University of Arizona’s Lunar and Planetary Laboratory.

McEwen is the principal investigator for the orbiter’s High Resolution Imaging Science Experiment (HiRISE) and the lead author of a report about the recurring flows published on August 5 by the journal Science.

Other explanations remain possible, but flows of liquid brine fit the features’ characteristics better than alternative hypotheses.

More than 1,000 flows seen

Saltiness lowers the temperature at which water freezes. Some sites with the dark flows get warm enough to keep water liquid if it is about as salty as Earth’s oceans, but temperatures in those areas would not melt pure water ice.

Sites with liquid brines could be important to future studies of whether life exists on Marsand to understanding the history of water.

Dark flows on Mars

Dark streaks change with the seasons on Mars.

The features are only about 0.5 to 5 metres wide, with lengths up to hundreds of metres. That’s much narrower than previously reported gullies on Martian slopes.

They have been seen in only about one percent as many locations as larger Mars gullies, but some of those locations display more than 1,000 individual flows. Also, while gullies are abundant on cold, pole-facing slopes, these dark flows are not.

Highly seasonal

The team first discovered the strange features after University of Arizona student Lujendra Ojha, at the time a junior majoring in geophysics, used a change detection algorithm capable of identifying subtle changes occurring on the Martian surface over time in image pairs during an independent study project.

“I was baffled when I first saw those features in the images after I had run them through my algorithm,” said Ojha, who is a co-author on the Science publication. “We soon realised they were different from slope streaks that had been observed before.

“These are highly seasonal, and we observed some of them had grown by more than 200 metres in a matter of just two Earth months.”

“By comparison with Earth, it’s hard to imagine they are formed by anything other than fluid seeping down slopes,” said Mars Reconnaissance Orbiter Project Scientist Richard Zurek of NASA’s Jet Propulsion Laboratory. “The question is whether this is happening on Mars and, if so, why just in these particular places.”

More clues

Other clues help, too. The flows lengthen and darken on rocky equator-facing slopes from late spring to early autumn. Favouring warm areas and times suggests a ‘volatile’ material is involved, but which volatile? The settings are too warm for carbon-dioxide frost and, at some sites, too cold for pure water.

This suggests the action of brines with their lower freezing points. Salt deposits indicate brines have been abundant in Mars’ past. These recent observations suggest they may form near the surface today in rare times and places.

Artist's impression of MRO

The streaks were spotted by NASA's Mars Reconnaissance Orbiter spacecraft (artist's impression).

Still a mystery

However, when researchers checked some flow-marked slopes with the orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), no sign of water appeared. The features may quickly dry on the surface, or be mainly shallow subsurface flows.

“The flows are not dark because of being wet,” McEwen said.

A flow initiated by briny water could rearrange grains or change surface roughness in a way that darkens the appearance. How the features brighten again when temperatures drop is harder to explain.

“It’s a mystery now, but I think it’s a solvable mystery with further observations and experiments,” he said.

Adapted from information issued by the University of Arizona. Images courtesy NASA / JPL / University of Arizona.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

Like this story? Please share or recommend it…

Mars is the pits

Pits on Mars

An image taken by NASA's Mars Reconnaissance Orbiter spacecraft reveals two huge, dark caves or pits on the Martian surface.

ENORMOUS, ALMOST-VERTICAL caves have been spotted on Mars by NASA’s Mars Reconnaissance Orbiter spacecraft.

The caves, or pits, measure 180 metres and 310 metres wide, and at first glance seem completely black.

But a closer inspection reveals details within. Scientists have enlarged the images and adjusted the contrast to bring out more details inside the pits.

Both pits shows boulders and sediments against the walls, with lighter-coloured wind-blown sand dunes on the floors.

Pit on Mars

An enhanced, enlarged view of the easternmost pit shows details within, including boulders and wind-blown sand dunes.

Pit on Mars

The westernmost pit is similar to its sibling. Both pits have steep eastern walls but more gently-sloped western walls.

In each case, the eastern walls of the pits are very steep while the western walls are more sloped, gradually merging into the floors.

Scientists will pour over these images to try to decipher the origin and geological history of the pits.

Images courtesy NASA / JPL / University of Arizona.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

Otherworldly artwork

Dust devil tracks on Mars

Tracks left by dust devils moving across the Martian dune plains.

These amazing patterns were spotted in the northern hemisphere of Mars on August 24, 2009 by the HiRISE camera aboard NASA’s orbiting Mars Reconnaissance Orbiter (MRO) spacecraft.

They are the tracks left by dust devils—mini tornadoes—moving across the Martian dunes.

Satellite image of a Martian dust devil

Looking down on a Martian dust devil...the small, round fuzz ball near the bottom left corner. The shadow cast by the devil can be seen to its left.

Take a look at the high-resolution version (will open in a new window or tab) of the image—it’s quite amazing.

Dust devils form when the Sun heats the surface so that the ground is warm to the touch, even though the atmosphere at 2 metres (6 feet) above the surface would be chilly. That temperature contrast causes convection (rising air) to where the wind speed is slightly higher. Mixing the dust, winds, and convection triggers the dust devils.

Scientists use images of dust devils to study several things. Tracking the devils shows which way the wind blows at different times of day. Statistics on the size of typical dust devils will help with estimates of how much dust they pump into the atmosphere every day. And by watching individual devils change as they go over more-dusty and less-dusty terrain, researchers can learn about the turbulent motion near the surface. Ultimately, that motion of wind and dust near the surface relates these small dust devils with Mars’ much larger dust storms.

MRO was 285 kilometres above the Martian surface at the time it took the image, which shows detail down to about 1.7 metres resolution.

The video below shows the progress of a dust devil moving across the plains in full view of the Spirit lander. The sequence of images spans a period of 9 minutes and 35 seconds, but has been speeded up for the purposes of the video.

Adapted from information issued by NASA / JPL-Caltech / Cornell University / Texas A&M / University of Arizona.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

Mapping Mars from orbit

Five years ago, NASA’s Mars Reconnaissance Orbiter was launched in search of evidence that water persisted on the surface of Mars over a prolonged period of time. Previous Mars missions indicated that, at some point in the Red Planet’s history, water flowed across its surface. Throughout the years, MRO has continued to analyse minerals, look for water, trace the distribution of dust in the atmosphere and monitor Martian weather.

Adapted from information issued by NASA.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz