Venus & Mars --- | ---
Outer Planets
Venus & Mars --- | ---
Outer Planets
Reading:
Chapter 5-4, 6-1 (ZG4)
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Key Question: | How did the gas giants get that way? |
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Key Principle: | Gravitational Energy |
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Key Problem: | How could Jupiter supply its power output of 4 x 1017 W? |
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Key Quote: | "Hey Jupiter!" |
As Mars approaches opposition once again, and thus its closest approach to Earth, two more spacecraft will be dispatched to the red planet as part of the NASA's Mars Exploration Program. The first of these, the Mars Climate Orbiter will enter its launch window on December 10, 1998! This is destined for a Mars orbit insertion on September 23, 1999. The second mission this M-year is the Mars Polar Lander which awaits its lauch window that starts January 3, 1999. MPL is scheduled to touch down on Mars on December 3, 1999. See the following sites for more details:
The Pathfinder mission was an astounding success! See the Pathfinder site for summary of the mission, including summary press release of the findings and science results.
In particular, though the camera provides us with the spectacular images, it is the Alpha Proton X-Ray Spectrometer (APXS) that measures the composition of the rocks and soil that the rover encounters. This instrument fires "alpha particles" which are high-velocity helium nuclei (2 protons & 2 neutrons bound together) at the target, and examines the energy signatures that come back. It can discern the elements in the rock by looking at the particles that are scattered back, from the X-ray emitted by the rock in response to excitation by the alpha particles, and by radioactivity due to nuclear reactions caused by the alpha particles interacting with light elements. This is loosely analogous to throwing pebbles at a bell, and looking at the way they bounce back, the sounds the bell makes, and possibly bits of the bell that are chipped off.
Check out the the amazing Mars globe image courtesy of the Mars Pathfinder page. Can you identify the features on the Mars globe? Where is the Mars Pathfinder landing site?
The Mars Global Surveyor (MGS) spacecraft has been sucessfully placed into an elliptical orbit around Mars. This is the second mission in NASA's ambitious Mars Exploration Program. Over the next 2 years, MGS will map the surface of the Red Planet in preparation for further missions. The Mars Global Surveyor Home Page is showing live telemetry and info - check it out!
NASA reported in 1997 that Martian meteorites contain possible microfossils. Much of the recent interest in Mars stems from the discovery of small carbonaceous nodules in a meteorite of Martian origin that may be signs of bacterial life earlier in the planet's history. This evidence is suggestive, though not conclusive, and is currently being disputed by several research groups.
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smyers@nrao.edu Steven T. Myers