Newly Released Mars Express Images Explore Nili Fossae
The European Space Agency’s Mars Express orbiter has probed a system of deep fractures on the Martian surface called Nili Fossae. Some of these cracks in the Martian crust, which are near the giant Isidis impact basin, are up to 500 meters deep. Scientists think that they formed about the same time as the basin was scoured out by an incoming impactor.
Nili Fossae is a “graben” system on Mars, northeast of the Syrtis Major volcanic province, on the northwestern edge of the giant Isidis impact basin. Graben refers to the lowered terrain between two parallel faults or fractures in the rocks that collapses when tectonic forces pull the area apart. The Nili Fossae system contains numerous graben concentrically oriented around the edges of the basin. Planetary scientists think that the nearby Isidis Basin was flooded with lava after the impact that created it. The weight of the lava caused the basin floor to subside, putting stress on the surrounding crust, which fractured to create Nili Fossae.
This system of grabens is of great interest to planetary researchers because this region also seems to have a connection to releases of methane into the atmosphere of Mars. They want to know if it is being produced somewhere in the region, and if so, what would be the source? Future missions to Mars will certainly want to study this area in greater detail to find out what’s happening here to release this greenhouse gas.
The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) announced Monday that they were going to team on a mission to Mars, called the ExoMars Trace Gas Orbiter or ExoMars for short. The announcement seeks “scientists to propose instruments to be carried on the mission.” The focus of the mission is to analyze “the rarest constituents of the martian atmosphere, including the mysterious methane that could signal life on Mars.” Learn more about the ExoMars mission online now here.
Last week there was a big splash (pun intended) made over some images taken by the Cassini spacecraft of Titan, Saturn’s largest moon. The images suggest that there is indeed liquid (liquid does not mean liquid water) on the surface of Titan. NASA has an excellent summary of the interpretation of the images online here, but please keep in mind that water has a number of unique properties. One of them is that water freezes from the top down, because frozen water floats in the liquid phase of water. Thus, here on Earth you can have frozen ponds with fish still swimming beneath. And on Europa you may find liquid water beneath the frozen solid surface top. Liquid ethane and methane don’t act in the same manner.
In a paper submitted to the Astrophysical Journal Letters, available online now here, astronomers announce the discovery of methane fog on Titan, specifically in the south polar region of Titan, during its summer. Summarized most succinctly these astronomers state that “based on the detections presented here, liquid methane
appears widespread at the south pole of Titan in late southern summer, and the hydrolgical cycle on Titan is currently active.”
In a paper published in Nature, available online now here, an international team of astronomers, utilizing the data from the Cassini spacecraft between 2004 and 2007, announce their conclusions about the nature of the clouds of Titan, Saturn’s largest and most interesting moon. These astronomers conclude that the clouds on Titan are the result of condensation of methane and ethane. Here on Earth, our clouds result from the condensation of water vapor. The clouds on Titan are driven around the moon by global atmospheric circulation. These astronomers have developed a global circulation model for Titan, similar to the global circulation models developed for Earth.
Most scientists involved with the science of astrobiology talk about the search in future exoplanet spectra for biosignatures of life. The three most often discussed are the carbon isotope ratio, free oxygen and most recently methane. Now in a paper submitted to the Astrophysical Journal, astronomers consider the usefulness of spectral detection of sulfur dioxide as a signature of a geochemical cycle on exoplanets. Read more about this proposed exoplanet geochemical signature online here.
In a seminar today, on the campus of George Mason University, Dr. Michael Summers provided graduate students and guests an overview of the latest developments in the quest and understanding of the search for methane in the atmosphere of Mars. The topic was chosen based upon an article that was originally published in the journal Science on 20 February 2009. This article by Mumma and others, is now available online to all at SpaceRef here. This seminar at GMU is also called the astrophysics journal club, run by Dr. Joe Weingartner. Graduate students usually take turn presenting recently published papers in astrophysics. This time, Dr. Summers was invited for his expertise on the subject of methane in the martian atmosphere. In fact, Dr. Summers’ paper published in 2002 was referenced in the Mumma paper. The main point is that if the findings of Mumma and others is valid, that is, methane exists in the atmosphere of Mars, it’s hard to explain how that methane got into the atmosphere unless there is an unusual geochemical process taking place or, wait for it, there is microbial life beneath the surface of Mars.
Earlier this week, astronomers utilizing the European Southern Observatory (ESO) Very Large Telescope released results of their observations of the dwarf planet Pluto.
The results are based upon occultations, that is observing distant star light pass through the atmosphere of Pluto, allowing astronomers to determine the chemical composition and temperature of portions of the atmosphere. Pluto has revealed itself to have a higher concentration of methane than originally thought, and this greenhouse gas leads to a higher atmospheric temperature than originally suggested. Learn more about the new revelations of the dwarf planet Pluto online now at http://www.eso.org/public/outreach/press-rel/pr-2009/pr-08-09.html
In today’s issue of Science, astronomers released data indicative of a large amount of methane released in the summer of 2003. Here on Earth, life is the generator of such amounts of methane and although it doesn’t mean that life generated the detected methane, it is one of the possible sources. Read more about this online at http://www.sciencemag.org/cgi/rapidpdf/1165243.pdf