As of late, my favorite TV channel to have on in the background is the NASA channel. In the next two blog postings I'll include information and images from the web page http://dawn.jpl.nasa.gov/ as well as some of the photos and concepts from the online rockhounding adventures.
The other day there was a documentary about NASA's Dawn Mission. Dawn is part of NASA’s Discovery Program. Its mission is to delve into the unknown, drive new technology innovations, and achieve what's never been attempted before. In Dawn’s case, it is orbiting two members of the main asteroid belt, Vesta and Ceres.
Dawn's goal is to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since the initial formation of our Solar System. Ceres and Vesta reside in the extensive asteroid belt located between Mars and Jupiter. Each has followed a very different evolutionary path and have been subjected to different processes that operated during the first few million years of solar system evolution. The top level question that the mission addresses is the role of size and water in determining the evolution of the planets. Ceres and Vesta are the right two bodies with which to address this question, as they are the most massive of the protoplanets, baby planets whose growth was interrupted by the formation of Jupiter. Ceres is very primitive and wet while Vesta is evolved and dry.
Dawn Mission Timeline
Launch September 27, 2007
Mars gravity assist February, 2009
Vesta arrival July, 2011
Vesta departure August, 2012
Ceres arrival February 2015
End of primary mission July 2015
The chart below shows the trajectory of the Dawn spacecraft.
Here are a couple of diagrams of the Dawn spacecraft.
This figure depicts the Dawn flight system.
HGA – High Gain Antenna
LGA – Low Gain Antenna
CSS – Coarse Sun Sensors
GRaND – Gamma Ray and Neutron Detector
IPS Thrusters – Ion Propulsion Thrusters
RCS Thrusters – Reaction Control System Thrusters
VIR – Visible and Infrared Mapping Spectrometer
FC – Framing Camera
The online rockhounding adventures cover the formation of the solar system in detail. But, in summary, in our corner of the Universe there was originally another star that met its end of life and blew up in a supernova explosion. The NASA image below shows what such an astronomical event would have looked like not long after the explosion.
After such an event, there is a lot of cosmic debris left over that forms into a nebula cloud of dust. Below are some actual Hubble telescope pictures of nebulae.
Over time, gravity and other physical laws caused this cosmic material left over from the supernova explosion to attract, condense, and start to spin -- sort of like a Frisbee spinning in space.
The spinning caused a lot of the material to migrate to the center and form our Sun.
The Sun had enough gravitational force to gather up most of the supernova remnants, but not all of it. The remaining space debris clumped together to form the planets.
In part because the processes that formed the four gas giant outer planets were different than those that formed the four inner planets, there is a zone in between with left over material -- the asteroid belt. The mission of Dawn is to visit the asteroid belt to learn more about it, and therefore learn more about the formation of our solar system.
Below is a picture of the launch of the Dawn spacecraft on September 27, 2007.
Below is an artist's drawing of the Dawn spacecraft.
Here is a picture of the first destination: Vesta.
Vesta, is one of the largest asteroids in the Solar System. Asteroids are small "planetoids" that orbit the Sun at the outer fringe of the inner Solar System between Mars and Jupiter. Asteroids can be either rocky or metallic, they have different amounts of water/ice, and they vary in other characteristics. Vesta is the second largest asteroid by mass after the dwarf planet, Ceres, which is the next destination for the Dawn mission. In terms of shear size, Vesta is the third largest since Ceres and Pallas are both larger. Vesta has a diameter of 326 miles (525 km) and contains 9 percent of the mass of all material in the asteroid belt. It was discovered by Heinrich Wilhelm Ojbers on 29 March 1807, and is named after the virgin goddess of home and hearth from Roman mythology. Vesta is the last remaining rocky protoplanet that has a differentiated interior similar to that found in the four terrestrial inner planets. Vesta is the brightest asteroid visible from Earth.
The Dawn spacecraft entered orbit around Vesta on 16 July 2011 for a one-year exploration, Dawn left Vestan orbit on September 5, 2012
As NASA's Dawn spacecraft left for its next destination,the photo of Vista above was compiled as a mosaic synthesized from some of the best photos taken during the one year study period. The towering mountain at the south pole — more than twice the height of Mount Everest — is visible at the bottom of the image. The set of three craters known as the "snowman" can be seen at the top left.
Sometime in the last billion years, Vesta collided with another planetoid. Scientists believe that this collision not only left an enormous crater in Vesta's southern hemisphere, but around one percent of Vesta's mass was blown into space, some of which has fallen to Earth. The image shows shows three slices of meteorites found on Earth that have been confirmed as originating from the giant asteroid Vesta. The meteorites, known as howardite, eucrite and diogenite meteorites, are shown above as they look when viewed through a polarizing microscope, where different minerals appear in different colors. The texture of the rocks reveals that they crystallized at different rates. The image on the left comes from a meteorite named QUE 97053 (Antarctica), which is basaltic eucrite. The image in the middle comes from the Moore County (North Carolina) cumulate eucrite. The image on the right comes from a diogenite meteorite named GRA 98108 (Antarctica).