The National Aeronautics and Space Agency is sending the Dawn space probe to investigate Ceres, now classified as a dwarf planet. The probe is currently investigating Vesta, an asteroid, and will reach Ceres in February, 2015. What will the probe find?
Already scientists know from spectrograph data that Ceres’ surface bears water ice. That fact is confirmed by Ceres’ high reflectivity.
Water ice and organics have already been confirmed on another asteroid, 24 Themis. The search for life always revolves around the definition of “life,” so if the definition is simple organics, life has already been discovered. Other missions found organic molecules in space.
Still, Ceres is intriguing because it may have subsurface water. Scientists made this educated guess by observing Ceres’ size with the Hubble Space Telescope or a similar instrument. Then, they observed slight changes in the orbits of Earth, Mars and other asteroids caused by Ceres’ gravity. From this they calculate Ceres’ density. Water has a lower density than rock or solid metals. Ceres’ estimated density is between the densities of water and rock. Therefore, scientists believe Ceres probably harbors water.
Of course, the water may be frozen.
According to the space agency, if Ceres “were composed of 25 percent water, it may have more water than all the fresh water on Earth.” The minor planet is about as wide across as Texas and may have frozen polar caps. The diameter changes as it orbits the Sun. Astronomer Fred Watson reports that at its minimum, the diameter is over 559 miles and 597 miles at maximum.
Italian astronomer Giuseppe Piazzi first discovered Ceres in 1801 and classified it as a planet. It was then reclassified as an asteroid. In 2006, the International Astronomical Union classified Ceres, Pluto, and Eris and “Dwarf Planets.”
SOURCES
Asteroid 1 Ceres, The Planetary Society
Detection of ice and organics on an asteroidal
Surface, Nature, April 29, 2010, Andrew S. Rivkin & Joshua P. Emery
Other Life Exists (book, 2010), Wade Hobbs
Dawn Mission pages, National Aeronautics and Space Agency
Astronomica (2007), Professor Fred Watson et al, pp. 106-07.