Mercury found to have comet-like appearance by satellites looking at sun

ROME and BOSTON - Scientists from Boston University's Center for Space Physics reported today that NASA satellites designed to view the escaping atmosphere of the Sun have also recorded evidence of gas escaping from the planet Mercury. The scientists reported these findings at the European Planetary Science Congress (EPSC) meeting in Rome, Italy this week.

The STEREO mission has two satellites placed in the same orbit around the Sun that the Earth has, but at locations ahead and behind it (STEREO, or Solar TErrestrial RElations Observatory, is the third mission in NASA's Solar Terrestrial Probes program). This configuration offers multi-directional views of the electrons and ions that make up the escaping solar wind. On occasion, the planet Mercury appears in the field of view of one or both satellites. In addition to its appearance as a bright disk of reflected sunlight, a "tail" of emission can be seen in some of the images. The announcement of this new method of observing Mercury and possible explanations for the nature of the gases that make up this tail were presented today at the EPSC.

It has been known that Mercury exhibits comet-like features, with a coma of tenuous gas surrounding the planet and a very long tail extending in the anti-sunward direction. From Earth, observations of both of these features can be done using light from sodium gas sputtered off the surface of Mercury. The Sun's radiation pressure then pushes many of the sodium atoms in the anti-solar direction creating a tail that extends many hundreds of times the physical size of Mercury. "We have observed this extended sodium tail to great distances using our telescope at the McDonald Observatory in Texas," Boston University graduate student Carl Schmidt explained, "and now the tail can also be seen from satellites near Earth." Much closer to Mercury, several smaller tails composed of other gases, both neutral and ionized, were found by NASA's MESSENGER satellite as it flew by Mercury in its long approach to entering into a stable orbit there.

"What makes the STEREO detections so interesting is that the brightness levels seem to be too strong to be from sodium," commented Schmidt, lead author on the paper presented at EPSC. Of special interest is the way the tail was spotted in the STEREO data by Ian Musgrave, a medical researcher in Australia who has a strong interest in astronomy. Viewing the on-line database of STEREO images and movies, Dr. Musgrave recognized the tail and sent news of it to Boston asking the BU team to compare it with their observations.

"A joint study was started and now we have found several cases, with detections by both STEREO satellites," explained Jeffrey Baumgartner, senior research associate in the Center for Space Physics at Boston University. Baumgartner designed of the optical instruments that discovered the exceptionally long sodium tail.

The current focus of the team is to sort out all of the possibilities for the gases that make up the tail. Christopher Davis, a researcher at the Rutherford Appleton Laboratory in Chilton, England and member of the STEREO team responsible for the camera systems on both satellites, is working closely with the Boston University group on refining brightness calibration methods and determining the precise wavelengths of light that would get through the cameras' filters.

"The combination of our ground-based data with the new STEREO data is an exciting way to learn as much as possible about the sources and fates of gases escaping from Mercury," said Michael Mendillo, professor of astronomy at Boston University and director of the Imaging Science Lab where the work is being done. "This is precisely the type of research that makes for a terrific Ph.D. dissertation," Mendillo added.

Research in Boston University's Center for Space Physics involves interdisciplinary projects between members of the Astronomy Department in the College of Arts and Sciences and faculty, staff and students in the College of Engineering. Research areas include observational and theoretical studies in atmospheric, ionospheric and magnetospheric physics, planetary and cometary atmospheres, solar and heliospheric physics, and space weather.

Founded in 1839, Boston University is an internationally recognized private research university with more than 30,000 students participating in undergraduate, graduate, and professional programs. As Boston University's largest academic division, the College and Graduate School of Arts & Sciences is the heart of the BU experience, creating an extensive global reach that enhances the University's reputation for teaching and research.

Figure 1: Image shows examples of the very long tails of sodium escaping from Mercury. These images were taken at the Boston University Station at the McDonald Observatory, run by the University of Texas in Austin. Reference: Orbital Effects on Mercury's Escaping Sodium Exosphere, Carl Schmidt, Jody Wilson, Jeffrey Baumgardner and Michael Mendillo, ICARUS, 2010.

Figure 2: A schematic representation of the viewing geometry that allows the STEREO camera systems to make observations of Mercury's tail.

Figure 3: An image of Mercury's tail obtained from combining a full day of data from a camera aboard the STEREO-A spacecraft. The reflected sunlight off the planet's surface results in a type of over-exposure that causes Mercury to appear much larger than its actual size. The tail-like structure extending anti-sunward from the planet is visible over several days and spans an angular size exceeding that of a full Moon in the night sky.

Figure 4: A movie showing a 4 day period when Mercury tail was visible from the STEREO A spacecraft on 6-9 February 2008.

Founded in 1839, Boston University is an internationally recognized institution of higher education and research. With more than 30,000 students, it is the fourth largest independent university in the United States. It contains 17 colleges and schools along with a number of multi-disciplinary centers and institutes which are central to the university's research and teaching mission

EPSC 2010 is organised by Europlanet, a Research Infrastructure funded under the European Commission's Framework 7 Programme, in association with the European Geosciences Union, with the support of the Italian National Institute for Astrophysics (INAF) and the INAF Institute of Physics of Interplanetary Science (IFSI) in Rome. EPSC is the major meeting in Europe for planetary scientists. The 2010 programme comprises 48 sessions and workshops covering a wide range of planetary topics.

EPSC 2010 is taking place at the Angelicum Center – Pontifical University of St. Thomas Aquinas, Rome, Italy from Sunday 19 September to Friday 24 September 2010.

For further details, see the meeting website: http://meetings.copernicus.org/epsc2010/

Europlanet Research RI is a major (€6 million) programme co-funded by the European Union under the Seventh Framework Programme of the European Commission.

Europlanet RI brings together the European planetary science community through a range of Networking Activities, aimed at fostering a culture of cooperation in the field of planetary sciences, Transnational Access Activities, providing European researchers with access to a range of laboratory and field site facilities tailored to the needs of planetary research, as well as on-line access to the available planetary science data, information and software tools, through the Integrated and Distributed Information Service. These programmes are underpinned by Joint Research Activities, which are developing and improving the facilities, models, software tools and services offered by Europlanet.

Europlanet Project website: http://www.europlanet-ri.eu/ Europlanet Outreach/Media website: http://www.europlanet-eu.org/

Michael Mendillo, professor of astronomy Center for Space Physics, Boston University Phone: +39 06 4891 3093 Email: mendillo@bu.edu

Carl Schmidt, graduate researcher Center for Space Physics, Boston University Phone: +1 617 353-5990 E-mail: schmidtc@bu.edu

Patrick Farrell, Communications Director College of Arts & Sciences, Boston University Phone: +1 617 358-1185; cell: +1 617-543-6480 E-mail: pmfarrel@bu.edu

Eleni Chatzichristou Europlanet Press Officer Phone: +30 697 2235681 E-mail: eleni.chatzichristou@europlanet-eu.org

Livia Giacomini INAF contact at Europlanet Press Office E-mail: livia.giacomini@ifsi-roma.inaf.it

The Moon Has A Comet-like Coma And Tail
by Phillip F. Schewe and Ben Stein
Physics News Update
American Institute of Physics Bulletin of Physics News
Number 36 (Story #5), May 31, 1991
Michael Mendillo of Boston University, reporting at this week's meeting of American Geophysical Union in Baltimore, showed that the moon has a tail, consisting of sodium gas, extending at least 15,000 miles away from the lunar surface. The sodium, Mendillo believes, is released from lunar rocks by meteorite impacts and is later dissipated into space where it is formed into a tail by the force of solar radiation.
Joint News Release
Boston University
Center for Space Physics
and American Geophysical Union
1 June 1999
Boston University astronomers announced today the discovery of an enormous tail of sodium gas stretching to great distances from the moon. The observations were made at the McDonald Observatory in Fort Davis, Texas, on nights following the Leonid meteor shower of November 1998. The tail of sodium gas was seen to distances of at least 500,000 miles from the moon, changing its appearance over three consecutive nights... Ten years ago, groundbased telescopes revealed that sodium gas (Na) was in the lunar atmosphere, an element that can be used to trace the shape and behavior of such a thin atmosphere... The BU team considered several theories that could explain these unusual features, ruling out a comet, the impact of Leonid meteors upon dust in the solar system, and even possible instrumentation problems... [T]he August observations without meteors and the November observations with meteors imply that the daily flux of micrometeors that strikes the moon's surface creates an extended tail at all times; it was just so enhanced during the strong Leonid storm that it was observed rather easily.
New Molecule Found In Comet May Unlock Solar System Origins
Space.com
Oct 15 1999 12:46:25 ET
The discovery of nitrogen sulfide (NS), a molecule known to exist within dense interstellar clouds, but previously unseen in a comet, may offer new clues to the origin of the solar system... The compound is the only known molecule in comets that contains both nitrogen and sulfur. The molecule is a "radical," which means that chemically, it is highly reactive... The discovery raises the question of whether the NS in comet Hale-Bopp (pictured here in a timed exposure with the moon) has existed since the start of the solar system, or if it was produced as a result of other compounds in the comet breaking apart... The way in which the abundance of NS varies in the comet's atmosphere -- or coma -- would indicate whether the molecule is the result of other compounds breaking apart due to the effect of sunlight, or whether it was produced by chemical reactions. To make such a determination, the NS molecule must be found in other comets.
Comets Throw Light On Solar System's Beginnings
Science Daily
Monday, September 8, 2008
A new picture of the composition of comets is emerging with the help of 21st century technology available at Diamond, the UK's national synchrotron light source, in Oxfordshire... Most of the icy, small planetary bodies that otherwise became comets went into forming the gas giant planets... a fraction ended up in the inner Solar System bringing water and biogenic elements of interest to Earth. Without this cometary transport, life on Earth may never have had a chance to start... Dr John Bridges, from the Space Research Centre, explains the results, "Comets are starting to look a lot more complicated than the old dusty iceball idea. For one thing Wild-2 contains material, like chromium oxides, from the hot inner Solar System -- so how did that material get mixed in with a comet which has spent most of its life beyond Neptune? ...we have also been finding X-ray signatures of iron oxides. These are important because they show that on the Wild-2 nucleus there could have been small trickles of water that deposited these minerals. Similar grains are found in carbonaceous chondrite meteorites. This might mean that there have been localised heating events perhaps caused by impact on the Wild-2 nucleus that melted some of its ice." ...Dr Bridges adds, "It's now becoming clear that not all comets are the same..."
Ingredients for Life on Earth May Have Been Delivered by Comets
by Mario Aguilera, Cindy Clark
2001
After obtaining a pristine piece of the interior portion of Orgueil, the researchers found that it contained a relatively simple mixture of amino acids, consisting primarily of glycine and beta-alanine. They also analyzed the sample's carbon isotope concentration and found that the amino acids were not derived from earthly contamination. "We found that the amino acids in Orgueil are abiotic. They were formed without the help of biology, only chemical reactions," said co-author Botta. "We think these amino acids were synthesized in space."

Thanks muawiyah. Here's some related archived oldies from the hard drive, probably in the area of 2001? I didn't check the save date...

Comet Cloud May Be Quite Thin
by Vanessa Thomas
In 1950, Dutch astronomer Jan Oort noticed these comets come from every direction and have orbits that reach about 50,000 astronomical units (AU) away from the sun. Paul Weissman of the Jet Propulsion Laboratory and Alan Stern of the Southwest Research Institute believe that many of the planetesimals that planetary scientists thought were ejected into the Oort Cloud actually were pulverized while still among the giant planets. Computer models by Stern and Weissman show that most of the large chunks and other debris were destroyed in collisions amongst themselves before the giant planets had a chance to use their gravitational influence to whip survivors out toward the solar system's edge.
Jupiter's Composition Throws Planet-formation Theories into Disarray
by Robert Roy Britt
Examining four-year-old data, researchers have found significantly elevated levels of argon, krypton and xenon in Jupiter's atmosphere that may force a rethinking of theories about how the planet, and possibly the entire solar system, formed. While lead researcher Tobias Owen does not put much stock in the idea that Jupiter might have migrated inward to its present position, other scientists on the team say the idea merits consideration. Owen expects the probes will find similarly high levels of noble gases in Saturn, Uranus and Neptune. Hints of these gases have even been found in the thick atmosphere of Venus, another planet now begging more study.

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