Ice that is at near freezing temperatures (273 K) and low pressure (<1 kbar) --Ice I-- has different physical properties than ice that is at lower temperatures and higher pressures. (e.g. Ice II is stable at 200 K and 6 kbar, while Ice VI is stable at 200 K and 15 kbar.) These phases of ice have different densities and flow properties that may be expressed through tectonic and volcanic processes on icy satellites. When these ices contain small amounts of "impurities" (e.g. ammonia) they are known as 'clathrates', and have a lower melting temperature than pure water-ice-- which may be a factor in volcanic processes on these satellites.
Low-phase is a small angle between the Sun, target, and
A low phase angle provides high sun illumination, similar to taking a picture from a high altitude at noon (with the sun directly overhead). Such illumination emphasizes the brightness contrasts of light and dark areas.
High-phase is a large angle between the Sun, target, and
A high phase angle provides low sun illumination, similar to taking a picture from a high altitude at sunset or sunrise. Such illumination emphasizes the topography of the terrain.
Materials with a high viscosity are more resistant to flow, while those with a low viscosity are more fluid.
Return to SSI Education and Public Outreach Homepage
Galileo Solid State Imaging Team Leader: Dr. Michael J. S. Belton
The SSI Education and Public Outreach webpages were originally created and managed by Matthew Fishburn and Elizabeth Alvarez with significant assistance from Kelly Bender, Ross Beyer, Detrick Branston, Stephanie Lyons, Eileen Ryan, and Nalin Samarasinha.
Last updated: September 17, 1999, by Matthew Fishburn
Return to Project Galileo Homepage
Website Curator: Leslie Lowes
Website Feedback: Ron Baalke