[meteorite-list] MRO Spacecraft Reveals a More Dynamic Red Planet

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?release=2013-361

NASA Mars Spacecraft Reveals a More Dynamic Red Planet
Jet Propulsion Laboratory
December 10, 2013

NASA's Mars Reconnaissance Orbiter has revealed to scientists slender 
dark markings -- possibly due to salty water - that advance seasonally 
down slopes surprisingly close to the Martian equator.  

"The equatorial surface region of Mars has been regarded as dry, free 
of liquid or frozen water, but we may need to rethink that," said Alfred 
McEwen of the University of Arizona in Tucson, principal investigator 
for the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science 
Experiment (HiRISE) camera. 

Tracking how these features recur each year is one example of how the 
longevity of NASA orbiters observing Mars is providing insight about changes 
on many time scales. Researchers at the American Geophysical Union meeting 
Tuesday in San Francisco discussed a range of current Martian activity, 
from fresh craters offering glimpses of subsurface ice to multi-year patterns 
in the occurrence of large, regional dust storms. 

The seasonally changing surface flows were first reported two years ago 
on mid-latitude southern slopes. They are finger-like features typically 
less than 16 feet (5 meters) wide that appear and extend down steep, rocky 
slopes during spring through summer, then fade in winter and return the 
next spring. Recently observed slopes stretch as long as 4,000 feet (1,200 
meters). 

McEwen and co-authors reported the equatorial flows at the conference 
and in a paper published online Tuesday by Nature Geoscience. Five well-monitored 
sites with these markings are in Valles Marineris, the largest canyon 
system in the solar system. At each of these sites, the features appear 
on both north- and south-facing walls. On the north-facing slopes, they 
are active during the part of the year when those slopes get the most 
sunshine. The counterparts on south-facing slopes start flowing when the 
season shifts and more sunshine hits their side. 

"The explanation that fits best is salty water is flowing down the slopes 
when the temperature rises," McEwen said. "We still don't have any definite 
identification of water at these sites, but there's nothing that rules 
it out, either." 

Dissolved salts can keep water melted at temperatures when purer water 
freezes, and they can slow the evaporation rate so brine can flow farther. 
This analysis used data from the Compact Reconnaissance Imaging Spectrometer 
for Mars and the Context Camera on the MRO as well as the Thermal Emission 
Imaging System experiment on NASA's Mars Odyssey orbiter. 

Water ice has been identified in another dynamic process researchers are 
monitoring with MRO. Impacts of small asteroids or bits of comets dig 
many fresh craters on Mars every year. Twenty fresh craters have exposed 
bright ice previously hidden beneath the surface. Five were reported in 
2009. The 15 newly reported ones are distributed over a wider range of 
latitudes and longitudes. 

"The more we find, the more we can fill in a global map of where ice is 
buried," said Colin Dundas of the U.S. Geological Survey in Flagstaff, 
Ariz. "We've now seen icy craters down to 39 degrees north, more than 
halfway from the pole to the equator. They tell us that either the average 
climate over several thousand years is wetter than present or that water 
vapor in the current atmosphere is concentrated near the surface. Ice 
could have formed under wetter conditions, with remnants from that time 
persisting today, but slowly disappearing." 

Mars' modern climate becomes better known each year because of a growing 
set of data from a series of orbiters that have been studying Mars continually 
since 1997. That has been almost nine Martian years because a year on 
Mars is almost two years long on Earth. Earlier missions and surface landers 
have added insight about the dynamics of Mars' atmosphere and its interaction 
with the ground. 

"The dust cycle is the main driver of the climate system," said Robert 
Haberle of NASA's Ames Research Center in Moffett Field, Calif. 

One key question researchers want to answer is why dust storms encircle 
Mars in some years and not in others. These storms affect annual patterns 
of water vapor and carbon dioxide in the atmosphere, freezing into polar 
ice caps in winter and replenishing the atmosphere in spring. Identifying 
significant variations in annual patterns requires many Martian years 
of observations. 

The data emerging from long-term studies will help future human explorers 
of Mars know where to find resources such as water, how to prepare for 
hazards such as dust storms, and where to be extra careful about contamination 
with Earth microbes. 

Launched in 2005, Mars Reconnaissance Orbiter and its six instruments 
have provided more high-resolution data about the Red Planet than all 
other Mars orbiters combined. Data are made available for scientists worldwide 
to research, analyze and report their findings. 

NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the MRO 
and Mars Odyssey missions for NASA's Science Mission Directorate in Washington. 
Lockheed Martin Space Systems in Denver built both orbiters. The University 
of Arizona Lunar and Planetary Laboratory operates the HiRISE camera, 
which was built by Ball Aerospace & Technologies Corp. of Boulder, Colo. 


For more information about NASA Mars exploration missions, visit: 
http://www.nasa.gov/mars 

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

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov 

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown at nasa.gov 

2013-361