The Hubble Ultra-Deep Field (HUDF) is an image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. The original release was combined from Hubble Space Telescope data accumulated over a period from September 24, 2003, through to January 16, 2004. Looking back approximately 13 billion years (between 400 and 800 million years after the Big Bang) it has been used to search for galaxies that existed at that time. The HUDF image was taken in a section of the sky with a low density of bright stars in the near-field, allowing much better viewing of dimmer, more distant objects. In August and September 2009, the HUDF field was observed at longer wavelengths (1. 0 to 1. 6 µm) using the infrared channel of the recently attached Wide Field Camera 3 (WFC3) instrument. When combined with existing HUDF data, astronomers were able to identify a new list of potentially very distant galaxies.
Each of the little Space eggs resides within its own ring arc--which is a fragmentary ring of Saturn. One hypothesis states that glittering ice crystals swarming around in the ring arc might be floating down to the surface of Methone, filling in its impact craters or other rough topography. This is something that is thought to have occurred on two other small, icy moons of Saturn--Atlas and Pan. Icy stuff swarming around in Saturn's rings apparently piled up around each moonlet's equator.
"We are just beginning to try and figure out quantitatively how all this might smooth a surface," Dr. Thomas said in the May 17, 2013 New Scientist.
The astronomers found that larger craters, which excavated pits much deeper into the Moon's surface, only increased porosity in the underlying crust. This indicates that these deeper layers have not reached a steady state in porosity, and are not as fractured as the megaregolith.