Seasonal flows on warm Martian slopes
Encyclopedia
Observations from NASA's Mars Reconnaissance Orbiter
have revealed possible flowing water
during the warmest months on Mars
. Research suggests that in the past there was liquid water flowing on the surface, creating large areas similar to Earth's oceans. However, the question remains as to where the water has gone. In a statement released by NASA
on August 4, 2011, repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show Recurring slope lineae (RSL), which are narrow (0.5 to 5 meters) and exhibit relatively dark markings on steep slopes, to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock
outcrops, often associated with small channels. RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes which favor equator-facing slopes, which are times and places with peak surface temperatures from −23 °C to 27 °C. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.
for NASA's Science Mission Directorate in Washington. The University of Arizona's Lunar and Planetary Laboratory operates HiRISE
. The camera was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Johns Hopkins University Applied Physics Laboratory in Laurel, Md., provided and operates CRISM
. JPL is a division of the California Institute of Technology in Pasadena.
distribution and brightness changes suggest a volatile
material is involved, but there is no direct detection of one. The settings are too warm for carbon-dioxide frost
and at some sites too cold for pure water. This suggests the action of brine
s, which have lower freezing points. Salt deposits over much of Mars indicate brines were abundant in Mars' past. These recent observations suggest brines still may form near the surface today in limited times and places.
According to NASA officials, the best explanation for these observations so far is the flow of briny water. Some aspects of these observations still puzzle researchers, but flows of liquid brine fit the features' characteristics better than other hypotheses. Since saltiness lowers the freezing temperature of water, sites with active flows get warm enough, even in the shallow sub-surface, to sustain liquid water that is about as salty as Earth's oceans, while pure water would freeze at the observed temperatures. These dark lineations appear different from other types of features on Martian slopes. Repeated observations have shown that they extend ever farther downhill with time during the warm season.
These results are the closest scientists have come to finding evidence of liquid water on the planet's surface today. Frozen water, however, has been detected near the surface in many middle to high-latitude regions. Fresh-looking gullies suggest slope movements in geologically recent times, perhaps aided by water. Purported droplets of brine also appeared on struts of the Phoenix Mars Lander in 2008. If further study of the recurring dark flows supports evidence of brines, these could be the first known Martian locations with liquid water.
Mars Reconnaissance Orbiter
Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...
have revealed possible flowing water
Water on Mars
Water on Mars is a psychedelic rock and electronic music group from Quebec City, Québec, Canada. The music trio is led by Philippe Navarro, guitarist, vocalist, arranger, producer, principal lyricist, and music composer....
during the warmest months on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. Research suggests that in the past there was liquid water flowing on the surface, creating large areas similar to Earth's oceans. However, the question remains as to where the water has gone. In a statement released by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
on August 4, 2011, repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show Recurring slope lineae (RSL), which are narrow (0.5 to 5 meters) and exhibit relatively dark markings on steep slopes, to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
outcrops, often associated with small channels. RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes which favor equator-facing slopes, which are times and places with peak surface temperatures from −23 °C to 27 °C. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.
Background
The Mars Reconnaissance Orbiter, which was launched in 2006, is managed by the Jet Propulsion Laboratory (JPL)Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
for NASA's Science Mission Directorate in Washington. The University of Arizona's Lunar and Planetary Laboratory operates HiRISE
HiRISE
High Resolution Imaging Science Experiment is a camera on board the Mars Reconnaissance Orbiter. The 65 kg , $40 million instrument was built under the direction of the University of Arizona's Lunar and Planetary Laboratory by Ball Aerospace & Technologies Corp....
. The camera was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Johns Hopkins University Applied Physics Laboratory in Laurel, Md., provided and operates CRISM
CRISM
The Compact Reconnaissance Imaging Spectrometer for Mars is a visible-infrared spectrometer aboard the Mars Reconnaissance Orbiter searching for mineralogic indications of past water on Mars. The CRISM instrument team comprises scientists from over ten universities and led by principal...
. JPL is a division of the California Institute of Technology in Pasadena.
Features
The features imaged are only about 0.5 to 5 meters wide, with lengths up to hundreds of meters. The width is much narrower than previously reported gullies on Martian slopes. However, 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 on warmer, equator-facing slopes. The images show flows lengthen and darken on rocky equator-facing slopes from late spring to early fall. The seasonality, latitudeLatitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
distribution and brightness changes suggest a volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...
material is involved, but there is no direct detection of one. The settings are too warm for carbon-dioxide frost
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...
and at some sites too cold for pure water. This suggests the action of brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...
s, which have lower freezing points. Salt deposits over much of Mars indicate brines were abundant in Mars' past. These recent observations suggest brines still may form near the surface today in limited times and places.
Dark flows
When researchers checked 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 could be shallow subsurface flows. Observations have also shown that the flows are not dark because of being wet. 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.Hypotheses
Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars' southern hemisphere.According to NASA officials, the best explanation for these observations so far is the flow of briny water. Some aspects of these observations still puzzle researchers, but flows of liquid brine fit the features' characteristics better than other hypotheses. Since saltiness lowers the freezing temperature of water, sites with active flows get warm enough, even in the shallow sub-surface, to sustain liquid water that is about as salty as Earth's oceans, while pure water would freeze at the observed temperatures. These dark lineations appear different from other types of features on Martian slopes. Repeated observations have shown that they extend ever farther downhill with time during the warm season.
These results are the closest scientists have come to finding evidence of liquid water on the planet's surface today. Frozen water, however, has been detected near the surface in many middle to high-latitude regions. Fresh-looking gullies suggest slope movements in geologically recent times, perhaps aided by water. Purported droplets of brine also appeared on struts of the Phoenix Mars Lander in 2008. If further study of the recurring dark flows supports evidence of brines, these could be the first known Martian locations with liquid water.
See also
- Water on MarsWater on MarsWater on Mars is a psychedelic rock and electronic music group from Quebec City, Québec, Canada. The music trio is led by Philippe Navarro, guitarist, vocalist, arranger, producer, principal lyricist, and music composer....
- Evolution of water on Mars and EarthEvolution of water on Mars and EarthThe evolution of water on either planet needs be understood in the context of the other terrestrial planetary bodies and their current water status.- Water Inventory of Mars:...
- Life on Mars
- Hydrology of Mars
- Water in the atmosphere of Mars
- Mars Express
- Mars Global Surveyor
- 2001 Mars Odyssey
- Presence of shallow subsurface water ice
- Extraterrestrial liquid waterExtraterrestrial liquid waterExtraterrestrial liquid water, the presence of water in its liquid state, is a subject of wide interest because it is a commonly suggested prerequisite for the emergence of extraterrestrial life....
- Mars Ocean HypothesisMars Ocean HypothesisThe Mars Ocean Hypothesis states that nearly a third of the surface of Mars was covered by an ocean of liquid water early in the planet’s geologic history....
- Colonization of MarsColonization of MarsThe colonization of Mars by humans is the focus of speculation and serious study because the surface conditions and availability of water on Mars make it arguably the most hospitable planet in the solar system other than Earth...
- Climate of MarsClimate of MarsThe climate of Mars has been an issue of scientific curiosity for centuries, not least because Mars is the only terrestrial planet whose surface can be directly observed in detail from the Earth....
- Extraterrestrial water vapor
- Extraterrestrial lifeExtraterrestrial lifeExtraterrestrial life is defined as life that does not originate from Earth...
External links
- NASA Picture Gallery on Seasonal flows on warm Martian slopes.