Jennifer LaVista ( Phone: 303-202-4764 );
Seasonal carbon dioxide frost, not liquid water, is the main driver in forming gullies on Mars today, according to a recent U.S. Geological Survey study that relied on NASA’s Mars Reconnaissance Orbiter’s (MRO) repeated high-resolution observations.
Martian gullies are landforms typically consisting of steep channels, usually having a recessed head, that feed into a fan of material deposited at the bottom. The discovery of active gullies was first reported in 2000, which generated excitement due to consideration that they might result from action of liquid water. Mars has water vapor and plenty of water ice, but liquid water, a necessity for all known life, has not been confirmed on modern Mars. The new report, published in the journal Icarus, is available online.
"As recently as five years ago, I thought the gullies on Mars indicated activity of liquid water," said USGS scientist Colin Dundas, lead author of the new report. "We were able to get many more observations, and as we started to see more activity and pin down the timing of gully formation and change, we saw that the activity is in winter."
A smaller type of seasonal flow seen on some slopes on Mars may involve liquid water, but is yet to be determined. These flows are called recurring slope lineae (RSL), and are sometimes found within small channels but not systematically associated with larger gullies.
Dundas and collaborators used the High Resolution Imaging Science Experiment (HiRISE) camera on MRO to examine each of 356 Martian sites with gullies at least twice, beginning in 2006. Thirty-eight of the sites showed activity, such as cutting a new channel segment or adding material to the apron-shaped deposit at the downhill end of a gully. Wherever the timing of before-and-after observations enabled determining the season of gully activity, it was a time too cold for the possibility of melting water-ice, but consistent with seasonal carbon dioxide frost.
"RSL and mass movements in Martian gullies are two distinct types of slope activity,” said Dundas “It's not hard to tell them apart in HiRISE images. The classic Martian gullies are much larger than RSL. Many of them are more the size that you'd call ravines on Earth."
Frozen carbon dioxide, commonly called dry ice, does not exist naturally on Earth, but it is plentiful on Mars. It has been linked to active processes on Mars such as geysers of carbon dioxide gas from springtime sublimation of dry ice, and blocks of dry ice that plow lines on sand dunes by sledding down dunes on cushions of sublimated gas. One mechanism for how carbon dioxide frost might drive gully flows is by gas that is sublimating from the frost, providing lubrication for dry material to flow. Another might be slides due to accumulating weight of seasonal frost buildup on steep slopes.
Work by Dundas and others has previously pointed to winter timing of gully formation on dune and non-dune slopes, with suggested involvement of seasonal changes in frozen carbon dioxide. The new report adds evidence for the changes. The findings also make a new point that the pace of gully formation that has now been documented is swift enough that all of the fresh-appearing gullies seen on Mars can be attributed to current processes. Some earlier hypotheses attributing the gullies to action of liquid water have suggested they formed thousands to millions of years ago when climate conditions were possibly more conducive to Mars having liquid water due to variations in the planet's tilt and orbit.
Dundas' co-authors on the new report are Serina Diniega of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, and Alfred McEwen of the University of Arizona, Tucson.
"Much of the information we have about gully formation and other active processes on Mars comes from the longevity of MRO and other orbiters,” said Diniega. “This enables repeated observation of sites to examine changes over time."
Data will appear in an upcoming special issue of Icarus with multiple reports about active processes on Mars, including RSL.
"I like that Mars can still surprise us," Dundas said. "Martian gullies are fascinating features where we can investigate a process that we just don't see on Earth."
HiRISE is operated by the University of Arizona. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. The Mars Reconnaissance Orbiter Project is managed for NASA's Science Mission Directorate, Washington, by JPL.
Visit the USGS Astrogeology Center to learn more.
Visit HiRISE for more information.
Additional information about MRO is available online.These two images show changes in a gully on Mars, and illustrate that these landforms are evolving rapidly. A rubbly flow (noted by the arrows) has been deposited near the mouth of the channel between the time of the two images. Further up the slope, the channel system has been modified by both erosion and deposition. The timing of such changes is often in winter or early spring, suggesting that they are caused by the carbon dioxide frost that forms in and around most gullies every year. (High resolution image)
ANCHORAGE, AK – Faith-based organizations in Anchorage and Fairbanks are welcoming hundreds of volunteers with open arms, providing them food, transportation and shelter as they prepare for the final leg of a journey to help rebuild communities hit by last year’s flooding and ice jams along the Yukon River. Armed with a wide range of construction skills, men and women from across the country began arriving in Fairbanks on the first of June and more arrived in Anchorage starting the first of July.Language English
JACKSON, Miss. – The Mississippi Emergency Management Agency and the Federal Emergency Management Agency remind survivors who registered for disaster assistance to stay in touch with FEMA.Language English
MONTGOMERY, Ala. – While the public may know the Federal Emergency Management Agency as the government entity that offers financial resources following disasters, FEMA is but one member of a team that brings much more.
Supporting the recovery is the coordinated effort of many federal, state and local partners, who together provide a wealth of programs and services to impacted communities and their residents.
ANCHORAGE, Alaska — Monitoring wildlife in the Arctic is difficult. Study areas are cold, barren and often inaccessible. For decades scientists have struggled to study animals, like polar bears, which live in these remote areas. Now researchers at the U.S. Geological Survey have begun testing a new, yet counterintuitive solution – rather then get close to the animals, monitor them from afar. Scientists have started using satellites to observe, count and track polar bears. USGS scientists and their Canadian collaborators have begun analyzing high-resolution satellite images from a part of the Canadian High Arctic to determine the feasibility of using satellites to study polar bear populations.
“We tested the use of satellite technology from DigitalGlobe to count polar bears by tasking the satellite to collect photos from an area where we were also conducting aerial surveys,” said Dr. Todd Atwood, research leader for the USGS Polar Bear Research Program. “We then analyzed the satellite and aerial survey data separately and found that the abundance estimates were remarkably similar.”
The study, which is led by former USGS scientist and current University of Minnesota researcher Dr. Seth Stapleton, is part of an ongoing effort to identify non-invasive technologies to better understand how polar bears respond to the loss of sea ice due to a warming climate. This study tries to determine the number of polar bears and where they reside on Rowley Island in Nunavut’s Foxe Basin during the ice-free summer. “We selected Rowley as our study site because bear density is high during summer and the flat terrain provides an ideal setting to evaluate the use of satellite imagery,” said Stapleton.
Traditionally, scientists study polar bears by capturing and tagging them or by conducting aerial surveys with low flying aircraft. While these methods provide a wealth of important information, they are disruptive to the animals and are often not possible when dealing with remote locations. “We think satellite technology has the potential to open vast, remote regions of the Arctic to regular monitoring. It has tremendous potential to aid the circumpolar management of polar bears,” said Stapleton.
The next steps in the research focus on testing the satellites’ ability to detect polar bear populations over larger areas, including sites along coastal Alaska. Using satellite imagery shows incredible promise and provides one more tool for those interested in preserving polar bear populations for future generations.
Following is a summary of key federal disaster aid programs that can be made available as needed and warranted under President Obama's disaster declaration issued for the State of New York.
Assistance for the State and Affected Local Governments Can Include as Required:Language English
WASHINGTON, D.C. – The U.S. Department of Homeland Security's Federal Emergency Management Agency announced that federal disaster aid has been made available to the State of New York to supplement state and local recovery efforts in the area affected by severe storms and flooding during the period of May 13-22, 2014.Language English
MONTGOMERY, Ala., -- Just one week remains to register for federal disaster assistance for those who sustained damage from the April 28 through May 5 severe storms, straight-line winds, tornadoes and flooding. The last day to register is Tuesday, July 15.
Residents who suffered damage should register as soon as possible. Here is how to register with FEMA:Language English
JACKSON, Miss. – Rebuilding or repairing property damaged from the recent severe storms? Residents in the Madison area can get advice on building safer and smarter from the Federal Emergency Management Agency.
Mitigation specialists from FEMA will be at Home Depot in Madison to offer information on rebuilding after a disaster. The advisers can answer questions about protecting homes from future disaster-related damage and offer tips to build hazard-resistant homes.Language English
RIDGELAND, Miss. — After a disaster, it takes many partners working together to rebuild communities. Two months after tornadoes and storms swept across the state on April 28, public, private and nonprofit organizations have made significant progress in responding to the needs of communities created by the disaster.Language English
DNREC Division of Fish and Wildlife seeking great summer shots of Delaware anglers for photo contest
MONTGOMERY, Ala. – The National Flood Insurance Program has extended the time period for filing flood claims for policyholders who experienced flooding during the April 28 through May 5 severe storms, tornadoes, straight-line winds and flooding.
The NFIP normally requires flood claims to be filed within 60 days of the date of loss. However, NFIP is waiving this requirement and extending the deadline by 30 days for the 2014 mid-spring storms that began on April 28. This extension includes policyholders in Alabama.Language English
MONTGOMERY, Ala. – Federal aid provided to Alabama residents affected by the April 28 through May 5 severe storms, tornadoes, straight-line winds and flooding has reached $34.5 million.
The following numbers, compiled July 3, provide a snapshot of the Alabama/FEMA disaster recovery to date:
Funds approvedLanguage English
Several large rivers in the U.S. are less acidic now, due to decreasing acidic inputs, such as industrial waste, acid mine drainage, and atmospheric deposition.
A USGS study showed that alkalinity, a measurement of a river's capacity to neutralize acid inputs, has increased over the past 65 years in 14 of the 23 rivers assessed in the U.S.
Reduced acidity levels were especially common in rivers in the Northeast, such as the Delaware and Schuylkill Rivers; the Midwest, such as the Illinois and Ohio Rivers; and the Missouri River in the Great Plains.
"Long-term monitoring of streamflow and water-quality is essential to track how changes in climate and land use are impacting rivers and how riverine inputs may impact valuable commercial and recreational fisheries in estuaries across the Nation," said William Werkheiser, associate director for water. "Increasing alkalinity levels in large rivers across the country since 1945 is a positive trend."
Acidification of U.S. rivers in the early part of the 20th century was mostly associated with these acid inputs, which reduced the alkalinity of some rivers and caused them to become more acidic.
Increased alkalinity concentrations in large rivers draining a variety of climate and land-use types in this country are an indicator of recovery from acidification.
By looking at changes in multiple chemicals, scientists conducting the study found that the alkalinity increases were due to decreasing acidic inputs. The reasons for decreased acidic inputs have been diverse and include greater regulation of industrial emissions and waste treatment and increased use of agricultural lime.
"This study shows us that our cumulative management actions over the last half century have reduced acidity levels in U.S. rivers," said lead author Edward Stets, research ecologist at the USGS. "Acidification of rivers that empty into estuaries can adversely impact shell-bearing organisms such as oysters and crabs."
This study was published in the journal Science for the Total Environment. Information on USGS long-term water-quality monitoring can be accessed at the National Water-Quality Assessment Program page.
FEMA: Preparedness for Hurricane Arthur Still Essential along Northeast Coast; Residents and Visitors Should Follow Direction of Local Officials
WASHINGTON -- The Federal Emergency Management Agency (FEMA) and its federal partners continue to monitor Hurricane Arthur’s impact and northward track. The agency encourages those in Arthur’s path to listen to their local officials, monitor storm conditions and take steps to be prepared.Language English