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From the NASA Astrobiology Institute Newsletter

20 August 2004
Earth, Mars, Europa, Titan, and other potentially habitable bodies in our solar system are continually exposed to the effects of their interplanetary and magnetospheric space environments. We invite contributions on direct or indirect astrobiological effects of natural and artificial space environment components (magnetic and electric fields, plasma, energetic particles and photons, radio and plasma waves, dust) on potentially habitable environments, and to related sites of pre-biotic organic synthesis in the solar system and the local interstellar medium. Presentations are also solicited on techniques exploiting space environment interactions (e.g., magnetospheric, auroral, atmospheric, surface) in searches for such environments within and beyond the Solar System.
Abstracts are due at the meeting web site, http://www.agu.org/meetings/fm04/, by September 1 for regular mail and by September 9 on-line. The journal Astrobiology has tentatively agreed to publish papers related to the theme of this session with manuscript submissions due by March 31, 2005. Please contact the conveners for further information (contact information is available at the web site).

From the NASA Astrobiology Institute Newsletter

20 August 2004
The American Geophysical Union 2004 Fall Meeting takes place 13-17 December 2004 in San Francisco.
Session B18: Evaluating the role of impact in the end Permian and end Traissic mass extinctions. How do these compare to other impact or extinction events?

Peter D. Ward (University of Washington), e-mail: argo@u.washington.edu.

Luann Becker (University of California Santa Barbara, Institute of Crustal Studies, Depepartment of Geological Sciences) e-mail: lbecker@crustal.ucsb.edu.

Frank T. Kyte (University of California Los Angeles, Center for Astrobiology, Institute of Geophysics and Planetary Physics), e-mail: kyte@igpp.ucla.edu.

This session will compare known evidence of impact in the stratigraphic record, such as the wealth of geochemical, mineralogical, and paleontological data from the Cretaceous/Tertiary and late Eocene events, to evaluate the possibility that impact was the sole, or an important component in the cause of the end Permian and end Triassic extinctions. We will specifically look at new information about possible meteoritic and impact tracers, as well as proposed craters, that have recently been invoked as evidence of impact related to the Permian extinction, and new data on the end Triassic extinction to assess the role of impact (if any) in these extinction events.
Additional information is available at the meeting web site, http://www.agu.org/meetings/fm04/.

From the NASA Astrobiology Institute Newsletter

20 August 2004
The 4th European Workshop on Exo/Astrobiology, "Life in Extreme Environments," will be held Monday, 22nd to Thursday, 25th November 2004 at the Walton Hall Campus of the Open University in Milton Keynes. For more information regarding the Workshop and how to register, please visit the web page at http://physics.open.ac.uk/eana/.

NASA/ESA releases

Cassini-Huygens Mission Status Report

NASA/JPL release 2004-208, 23 August 2004

The Cassini spacecraft successfully completed a 51-minute engine burn that will raise its next closest approach distance to Saturn by nearly 300,000 kilometers (186,000 miles). The maneuver was necessary to keep the spacecraft from passing through the rings and to put it on target for its first close encounter with Saturn's moon Titan on October 26.
Mission controllers received confirmation of a successful burn at 11:15 AM Pacific Time today. The spacecraft is approaching the highest point in its first and largest orbit about Saturn. Its distance from the center of Saturn is about 9 million kilometers (5.6 million miles), and its speed just prior to today's burn was 325 meters per second (727 miles per hour) relative to Saturn. That means it is nearly at a standstill compared to its speed of about 30,000 meters per second (67,000 miles per hour) at the completion of its orbit insertion burn on June 30.
"Saturn orbit insertion got us into orbit and this maneuver sets us up for the tour," said Joel Signorelli, spacecraft system engineer for the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, CA.
The maneuver was the third longest engine burn for the Cassini spacecraft and the last planned pressurized burn in the four-year tour. The Saturn obit insertion burn was 97 minutes long, and the deep space maneuver in December 1998 was 88 minutes long.
"The October 26 Titan encounter will be much closer than our last one. We'll fly by Titan at an altitude of 1,200 kilometers (746 miles), 'dipping our toe' into its atmosphere," said Signorelli. Cassini's first Titan flyby on July 2 was from 340,000 kilometers (211,000 miles) away.
Over the next four years, the Cassini orbiter will execute 45 Titan flybys as close as approximately 950 kilometers (590 miles) from the moon. In January 2005, the European-built Huygens probe that is attached to Cassini will descend through Titan's atmosphere to the surface.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, DC. JPL designed, developed and assembled the Cassini orbiter.
Cassini-Huygens Periapsis Raising Maneuver

ESA release, 24 August 2004

The Cassini-Huygens spacecraft has successfully performed its scheduled Periapsis Raising Maneuver (PRM). A 51-minute burn of the primary engine corrected the spacecraft trajectory to place it on a course to encounter Saturn’s largest moon, Titan, in October. The maneuver also raised the periapsis (point of closest approach to Saturn) by over 400 000 km. Prior to the PRM the Cassini-Huygens spacecraft had been in a highly elliptical orbit around Saturn following the SOI maneuver of 1 July. The orbital elements with respect to Saturn's equatorial plane were:

Semi-major axis: 4,585,959 km

Eccentricity: 0.98239

Periapsis radius: 80,731 km

Apoapsis radius: 9,091,186 km

Inclination: 11.534°

If left in this orbit the spacecraft would not encounter Titan with the correct velocity to make further orbital changes for the successful deployment of the Huygens probe, and would return to a periapsis point 20,000 km above Saturn's cloud tops and also a second ring plane crossing.
The PRM was performed when Cassini-Huygens was near the outer point in its orbit at about 9 million kilometers from Saturn. Here the orbital velocity had reduced to a mere 325 ms-1 compared to the 30,000 ms-1 after the SOI engine burn on 30 June. The PRM engine burn imparted an increase in the orbital velocity of between 350 and 390 ms-1. Later confirmation will give the exact new orbital parameters which were targeted to be:

Semi-major axis: 4,790,340 km

Eccentricity: 0.896

Periapsis radius: 498,970 km

Apoapsis radius: 9,081,700 km

Inclination: 12.83°

The new periapsis is located in the safe, tenuous outer regions of Saturn’s E-ring instead of only 20,000 km above Saturn’s cloud tops. This periapsis is of little significance because the Titan encounter on 26 October, at an altitude of only 1200 km, will change the orbital parameters again.
Titan Encounters
During the first three orbits around Saturn (Orbit A, B and C) Cassini-Huygens will make three encounters with Titan. The Huygens probe will be released on 25 December 2004 to descend in Titan's atmosphere on 14 January 2005.

First three orbits after SOI with 3 Titan flybys and the Huygens Probe Release. [http://sci.esa.int/science-e-media/img/7d/PRM-390.gif]
Read the original news release at http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=35709.
Cassini Significant Events for 19-25 August 2004

NASA/JPL release, 27 August 2004

The most recent spacecraft telemetry was acquired from the Madrid tracking station on Wednesday, August 25. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm.

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