About the Future and Current Exploration of SSSBs
I do realize that I was about to fail already on my new year resolution which was to write 2 posts at least per week on this blog. My sincere apologize for that, this week has been extremely busy. On Monday and Tuesday of last week, I was a Washington DC to attend the first SBAG meeting. I think you may be interested to hear about what are the future and current status of exploration for Small Solar System Bodies.
I did not really know what to expect of this meeting since it was the first time that our community of small solar body exploration met in the framework of a NASA assessment group. The goal of this meeting was indeed to put together people who work in our field and provide recommendations to NASA for the future space exploration. Jim Green, the director of Planetary Science Division, gave the first speech. He clearly emphasized the need for NASA to get connection with the science community and for us to be more involved in their mission design process. Lindley Johnson, head of the Discovery program gave an extremely interesting talk about the sear and study for Near Earth Objects (NEOs). I will go back to that in my next post most likely.
The rest of the first day included reviews describing the status of previous and future missions. Mike A’Hearn from University of Maryland talked about Deep Impact which was renamed EPOXY for its extended mission. You must have heard about Deep Impact which successfully flyby and impact comet Tempel 1 on July 4 2005. One of the orbiter is still active and it will be used to flyby another comet called 103 P/Halley 2 in November 2010. NASA quite often recycles a spacecraft if the instruments are still functioning and if there is enough propellant to send it close to an interesting target. We have collected closed snapshot of only comet nuclei and they are all different in size, composition, shape and features on the surface. The visit of a new one will be definitely useful to understand how these bodies formed and evolved. Interestingly, the mission Stardust, known for having visited the comet Wild-2 and collected a sample of its environment in 2001 (the capsule full of inter-planetary materials landed on Earth in 2006) is now en-route toward the comet Tempel 1. The spacecraft will arrive on Feb 14 2011 at proximity of the comet nucleus and will image the crater of the impact with Deep Space 1 (we did not see it since the instruments were saturated during the impact) and see any other surface changes almost exactly one orbit after Deep Space 1 encounter. It is very exciting and encouraging to see the engineers at NASA can recycle their missions to improve our knowledge of small solar sytem bodies. This is possible mostly because the spacecrafts are well designed and after completing their primary mission they can be still used.
There was also another talk given by P. Weissman (JPL) about Rosetta, one of corner-stone missions of ESA (European Space Agency). This is definitely one of the most ambitious spacecrafts for the exploration of the primitive bodies. The spacecraft launched in March 2004 using an Ariane 5, had a recent flyby of the asteroid 2867 Stein , also called a Diamond in the Sky by ESA astronomer (beginning of September 2008). It will continue his mission with a flyby of a large asteroid called 21 Lutetia in July 2010. Lutetia is an intriguing object, its taxonomic class is unknown. It could have the same composition than carbonaceous chondrite meteorite (C-type) or made mostly of Iron and Nickel like metallic meteorite (M-type). The data collected by Rosetta instruments will most likely tell us more about this asteroid and its formation. There are 21 instruments on board Rosetta and its lander, including 2 from US-based institutions, so this definitely a first class spacecraft. After a long period of inactivity Rosetta will have a rendezvous with the comet 67P/Churyumov- Gerasimenko in May 2014! A lander called Philae will reach the surface and make in-situ measurements of the comet nucleus. We just have to wait for 5 years to see what the surface of a comet is made of. I wonder if it looks like the one that you may have seen in the movie called Armageddon.
I also really liked the talk given by Lucy McFadden from University of Maryland about the Dawn mission. Dawn is the 9th discovery mission of NASA (I need to find the list of the previous 8 missions). It was launched on September 27 2007 using an Delta-II. After a long journey of 8 years with one gravity assist encounter with Mars in Feb 2009, the mission will have rendezvous with Vesta. This is large asteroid and the spacecraft will remain in orbit around it from Aug 2011 to May 2012 to extensively study it using its 3 main instruments (Framing camera, Vis-NIR spectrograph and Gamma-ray/Neutron spectrometer). It will use its ion propulsion thruster to leave the orbit and cruise toward Ceres, the largest main-belt asteroid. These two targets are very special among the 320,000 asteroids of the main-belt. 4 Vesta (4th asteroid discovered in 1807) is the second most massive object in the asteroid main-belt (D~530 km). It has a surface characterized by the presence of mafic materials (same as lava of Earth volcanoes). Its spectra in visible and near infrared is very different than other asteroids. We think that Vesta is a piece of an already differentiated larger body which was disrupted and we are discovering more asteroids with the same composition (V-type) which are most likely fragments of this disruption. 1 Ceres is the first asteroid discovered in the main-belt by G. Piazzi in 1801 and the largest one in the main-belt (D=1000 km). It was thought to be a planet for a while, but was then demoted to the minor planet category (something familiar?) when astronomers discovered that thousands of other bodies orbit between Mars and Jupiter forming the main-belt of asteroids. In August 2006,, Ceres was classified as a dwarf planet by astronomers because of its almost spherical shape which is close to equilibrium due to self-gravity. Dawn will have rendezvous with Ceres in February 2015 and remain in orbit around the asteroid for 6 months.