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Астронет: Астрономическая картинка дня Необычный валун на пике Тихо http://variable-stars.ru/db/msg/1409061/eng |
Credit & Copyright: NASA,
Arizona State U.,
LRO;
Upper Inset:
NASA,
Arizona State U.,
LRO;
Lower Inset:
Gregory H. Revera
Explanation:
Why is there a large boulder near the center of Tycho's peak?
Tycho crater on
the Moon is one of the easiest features to see,
visible even to the unaided eye (inset, lower right).
But at the
center of Tycho (inset, upper left) is a something unusual -- a 120-meter boulder.
This boulder was imaged at very high resolution
at sunrise, over the past decade,
by the Moon-circling
Lunar Reconnaissance Orbiter
(LRO).
The leading origin hypothesis is that that the boulder was thrown during the
tremendous collision that formed Tycho crater about 110
million years ago, and by chance came back down right near the center of the
newly-formed central mountain.
Over the next billion years meteor impacts and
moonquakes should slowly degrade
Tycho's center, likely
causing the central boulder to tumble 2000 meters down to the
crater
floor and disintegrate.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.