New clues are emerging about the mysterious streaks that appear on Mars' surface during warm weather, though scientists still can't say for sure that they're caused by flowing water.
The marks, known as recurring slope lineae (RSL), snake down some crater walls and other inclines when the mercury rises on the Red Planet. New research finds seasonal changes in iron minerals at RSL sites, suggesting that brines containing an iron antifreeze may flow there from time to time — but direct evidence of water remains elusive.
This image combines a photograph of seasonal dark flows on a Martian slope with a grid of colors based on data collected by a mineral-mapping spectrometer observing the same area. Image released Feb. 10, 2014.
"We still don't have a smoking gun for existence of water in RSL, although we're not sure how this process would take place without water," Lujendra Ojha, a graduate student at Georgia Tech in Atlanta, lead author of two recent RSL studies, said in a statement. (Ojha discovered the RSL in 2011, while an undergraduate at the University of Arizona.) [Photos: The Search for Water on Mars]
Dark, seasonal flows emanate from bedrock exposures at Palikir Crater on Mars in this image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Three arrows point to bright, smooth fans left behind by flows. This image was taken on June 27, 2011 and released on Feb. 10, 2014.
Ojha and his colleagues studied images of 13 RSL sites taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), an instrument aboard NASA's Mars Reconnaissance Orbiter (MRO). They saw relatively high concentrations of iron minerals at most of the sites.
"Just like the RSL themselves, the strength of the spectral signatures varies according to the seasons," Ojha said. "They're stronger when it's warmer and less significant when it's colder."
Many scientists think the recurring slope lineae are created by water flowing just beneath the Martian surface. This water — which would leave the iron antifreezes and other minerals in its wake — likely contains salts that lower its freezing point significantly, allowing it to stay liquid despite frigid Red Planet temperatures.
While the researchers didn't see any spectral signatures of water in the CRISM images, that doesn't rule out the substance's presence at RSL sites, scientists said.
For example, the observations were made exclusively in the afternoon and thus could have missed surface water appearing in the morning. Further, each CRISM image observed a large area, possibly making it tough to spot signs of water in the narrow RSL streaks.
The researchers reported these results late last year in the journal Geophysical Research Letters. In another study, due out next month in the journal Icarus, a team led by Ojha analyzed pictures snapped by MRO and NASA's Mars Odyssey orbiter, looking for patterns in RSL formation on the Red Planet.
The team found 200 locations where conditions seemed ideal for seasonal streaks — areas in the southern mid-latitudes with rocky cliffs — but found only 13 with actual RSL marks.
"The fact that RSL occur in a few sites and not others indicates additional unknown factors such as availability of water or salts may play a crucial role in RSL formation," Ojha said.
Unraveling the mystery of Mars' seasonal dark lines could reveal exciting things about the Red Planet, such as its potential to host life as we know it, NASA officials said.
"The flow of water, even briny water, anywhere on Mars today would be a major discovery, impacting our understanding of present climate change on Mars and possibly indicating potential habitats for life near the surface on modern Mars," MRO project scientist Richard Zurek, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.
Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.
Copyright 2014 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Our 2024 Coverage Needs You
It's Another Trump-Biden Showdown — And We Need Your Help
The Future Of Democracy Is At Stake
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
The 2024 election is heating up, and women's rights, health care, voting rights, and the very future of democracy are all at stake. Donald Trump will face Joe Biden in the most consequential vote of our time. And HuffPost will be there, covering every twist and turn. America's future hangs in the balance. Would you consider contributing to support our journalism and keep it free for all during this critical season?
HuffPost believes news should be accessible to everyone, regardless of their ability to pay for it. We rely on readers like you to help fund our work. Any contribution you can make — even as little as $2 — goes directly toward supporting the impactful journalism that we will continue to produce this year. Thank you for being part of our story.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
It's official: Donald Trump will face Joe Biden this fall in the presidential election. As we face the most consequential presidential election of our time, HuffPost is committed to bringing you up-to-date, accurate news about the 2024 race. While other outlets have retreated behind paywalls, you can trust our news will stay free.
But we can't do it without your help. Reader funding is one of the key ways we support our newsroom. Would you consider making a donation to help fund our news during this critical time? Your contributions are vital to supporting a free press.
Contribute as little as $2 to keep our journalism free and accessible to all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you'll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.