Difference between revisions of "April 2, 2004"
(Created page with "__NOTOC__ =Interplanetary Comparisons= ---- ===COMMENTS?=== Click on this icon image:PostIcon.jpg at the upper right to post a comment.") |
|||
| (8 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
__NOTOC__ | __NOTOC__ | ||
=Interplanetary Comparisons= | =Interplanetary Comparisons= | ||
| − | + | <!-- Start of content --> | |
| − | + | <table width="85%" border="0" align="center" cellpadding="6" cellspacing="2"> | |
| − | + | <tr> | |
| − | ---- | + | </tr> |
| − | === | + | </table> |
| − | + | <table width="85%" border="0" align="center" cellpadding="6" cellspacing="2"> | |
| + | <tr> | ||
| + | <td colspan="2"><div align="center"> | ||
| + | [[File:LPOD-2004-04-02.gif|LPOD-2004-04-02.gif]]</div> | ||
| + | </td> | ||
| + | </tr> | ||
| + | </table> | ||
| + | <table width="100%" border="0" cellpadding="8"> | ||
| + | <tr> | ||
| + | <td><div align="center"><p>Image Credit: [mailto:robinson@eros.earth.northwestern.edu Mark Robinson]</p></div></td> | ||
| + | </tr> | ||
| + | </table> | ||
| + | <table class="story" border="0" bgcolor="#FFFFFF" width="90%" cellpadding="10" align="center"><tr><td> | ||
| + | <p class="story" align="center"><b>Interplanetary Comparisons - Mercury Photo of the Day </b></p> | ||
| + | <p class="story" align="left"> I tricked you - or tried to. Yesterday's April 1st LPOD wasn't really of unidentified craters on the Moon, but | ||
| + | was of the planet Mercury, taken by the Mariner 10 spacecraft during flybys in 1974/75. The craters do look very | ||
| + | similar to lunar craters because the hypervelocity impact process that forms craters is remarkably similar | ||
| + | throughout the solar system. Impact craters are so much alike that differences can provide clues about physical | ||
| + | or historical differences between planets. One important physical difference between Mercury and the Moon is that | ||
| + | Mercury's gravity is more than twice as strong (370 cm/sec<sup>2</sup> vs 162 cm/sec<sup>2</sup>). The greater | ||
| + | gravity reduces the flight distance of ejecta from impacts, leading to secondary craters and associated rays | ||
| + | being closer to the crater rim. Higher impact velocities for Mercury lead to craters being deeper than on the | ||
| + | Moon. An important historical difference between the Moon and Mercury affects the differences in the | ||
| + | concentration of craters. In the lunar highlands and on the farside, craters have been accumulating for about 4.4 | ||
| + | billion years - there are few empty spaces. On Mercury, spaces between craters led to the suggestion that lava | ||
| + | flows were erupted through out the early stages of Mercury's history, erasing earlier craters. There are many | ||
| + | other interesting things to say about Mercury, but even more is coming. Mercury | ||
| + | [http://messenger.jhuapl.edu/ Messenger] is a spacecraft to be launched to Mercury this summer. | ||
| + | People with great patience can marvel at its discoveries on its arrival in 2011! Finally, most people, even | ||
| + | astronomers, have never seen Mercury with their own eyeballs. Tonight you can | ||
| + | [http://skyandtelescope.com/observing/ataglance/article_110_1.asp observe] Mercury low in the west | ||
| + | after sunset. | ||
| + | </p> | ||
| + | <blockquote> | ||
| + | <p align="right" class="story">— [mailto:tychocrater@yahoo.com Chuck Wood]</p> | ||
| + | </blockquote> <p><b>Technical Details:</b><br> | ||
| + | The left side image in yesterday's LPOD shows the southern tip of the Michelangelo Quadrangle of | ||
| + | Mercury. The rays come from a bright, apparently unnamed crater in the Bach Quadrangle. The right | ||
| + | side image shows the 130 km wide Sotatsu crater in the Discovery Quadrangle. Both images - and | ||
| + | today's incoming mosaic are from Mark's | ||
| + | [http://cps.earth.northwestern.edu/M10/image_archive.html site]. | ||
| + | </p> | ||
| + | <p class="story"><b>Related Links:</b><br> | ||
| + | [http://cps.earth.northwestern.edu/merc.html MERCURY Mariner 10 Image Project]<br> | ||
| + | [http://history.nasa.gov/SP-423/mariner.htm NASA Atlas of mercury]<br> | ||
| + | [http://www.astro.uu.se/planet/planet/Merkurius/mercury95.html High Res Mercury Images from Earth] | ||
| + | </p> | ||
| + | <p><b>Yesterday's LPOD:</b> [[April 1, 2004|What Part of the Moon is This?]] </p> | ||
| + | <p><b>Tomorrow's LPOD:</b> [[April 3, 2004|Mercy, Mersenius!]] </p> | ||
| + | </td> | ||
| + | </tr> | ||
| + | </table> | ||
| + | <!-- start bottom --> | ||
| + | <hr align="center" width="640"> | ||
| + | <p align="center" class="main_titles"><b>Author & Editor:</b><br> | ||
| + | [mailto:tychocrater@yahoo.com Charles A. Wood]</p> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <!-- Cleanup of credits --> | ||
| + | <p> </p> | ||
| + | <!-- End of content --> | ||
| + | {{wiki/ArticleFooter}} | ||
Latest revision as of 19:14, 7 February 2015
Interplanetary Comparisons
 |
Image Credit: Mark Robinson |
|
Interplanetary Comparisons - Mercury Photo of the Day I tricked you - or tried to. Yesterday's April 1st LPOD wasn't really of unidentified craters on the Moon, but was of the planet Mercury, taken by the Mariner 10 spacecraft during flybys in 1974/75. The craters do look very similar to lunar craters because the hypervelocity impact process that forms craters is remarkably similar throughout the solar system. Impact craters are so much alike that differences can provide clues about physical or historical differences between planets. One important physical difference between Mercury and the Moon is that Mercury's gravity is more than twice as strong (370 cm/sec2 vs 162 cm/sec2). The greater gravity reduces the flight distance of ejecta from impacts, leading to secondary craters and associated rays being closer to the crater rim. Higher impact velocities for Mercury lead to craters being deeper than on the Moon. An important historical difference between the Moon and Mercury affects the differences in the concentration of craters. In the lunar highlands and on the farside, craters have been accumulating for about 4.4 billion years - there are few empty spaces. On Mercury, spaces between craters led to the suggestion that lava flows were erupted through out the early stages of Mercury's history, erasing earlier craters. There are many other interesting things to say about Mercury, but even more is coming. Mercury Messenger is a spacecraft to be launched to Mercury this summer. People with great patience can marvel at its discoveries on its arrival in 2011! Finally, most people, even astronomers, have never seen Mercury with their own eyeballs. Tonight you can observe Mercury low in the west after sunset. Technical Details: The left side image in yesterday's LPOD shows the southern tip of the Michelangelo Quadrangle of Mercury. The rays come from a bright, apparently unnamed crater in the Bach Quadrangle. The right side image shows the 130 km wide Sotatsu crater in the Discovery Quadrangle. Both images - and today's incoming mosaic are from Mark's site. Related Links: Yesterday's LPOD: What Part of the Moon is This? Tomorrow's LPOD: Mercy, Mersenius! |
Author & Editor:
Charles A. Wood
COMMENTS?
Register, Log in, and join in the comments.
