collapse lava tubes as opposed to impact chains [oh darn]
Jerry Flaherty
----- Original Message -----
From: "Sterling K. Webb" <[EMAIL PROTECTED]>
To: "Meteorite Mailing List" <[email protected]>
Cc: "Gerald Flaherty" <[EMAIL PROTECTED]>; "Ron Baalke"
<[EMAIL PROTECTED]>; "Larry Lebofsky" <[EMAIL PROTECTED]>
Sent: Wednesday, January 16, 2008 10:24 PM
Subject: Re: [meteorite-list] Two New Images from MESSENGER's First
FlybyofMercury
Hi, Jerry,
That is the received wisdom derived from study of
our Moon, that bright rayed craters are fresher. I would
think that it would be truer on Mercury than the Moon,
as the UV intensity and the strength of the solar wind
should darken them faster. You could probably get a
great tan and a light microwaving in no time on Mercury.
There are a multitude of teeny craters like freckles
and lots of very crisp small craters, while most of
the medium and large craters do not look fresh. In the
very first closeup picture released, there was a good sized
crater with a brighter fresher crater 60% of its size almost
dead center inside of it!
How many impacts that size do you have to have to
get two shots on dead center? Lots. I've been flipping
through pictures of other surfaces to see if I can find
another example like that and, so far, I can't. The crater-
counters will have a field day!
It's also surprising how many linear crater alignments
there are. There will be a repeat of the arguments from
lunar days of whether they are Shoemaker-Levy-style
multi-impact chains or collapsed lava tubes.
Mercury only looks like the Moon at a casual glance.
Even in the old Videcon TV pictures of Mariner 10,
it looked strange. In these closer, much more detailed
images, it looks even stranger. Lots of collapse features.
There may be more vulcanism than we think likely.
Ah! There's a good argument!
Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: "Jerry" <[EMAIL PROTECTED]>
To: "Ron Baalke" <[EMAIL PROTECTED]>; "Meteorite Mailing List"
<[email protected]>
Sent: Wednesday, January 16, 2008 8:55 PM
Subject: Re: [meteorite-list] Two New Images from MESSENGER's First
Flybyof
Mercury
Do the bright rays indicate a more "recent" impact?
Jerry Flaherty
----- Original Message -----
From: "Ron Baalke" <[EMAIL PROTECTED]>
To: "Meteorite Mailing List" <[email protected]>
Sent: Wednesday, January 16, 2008 8:36 PM
Subject: [meteorite-list] Two New Images from MESSENGER's First Flyby of
Mercury
http://messenger.jhuapl.edu/news_room/status_report_01_16_08_2.html
MESSENGER Mission News
January 16, 2008 [Evening Update]
Two New Images from MESSENGER's First Flyby of Mercury
Detailed Close-up of Mercury's Previously Unseen Surface
Just 21 minutes after MESSENGER's closest approach to Mercury on January
14, 2008, the Narrow Angle Camera (NAC) took this picture
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=119>
showing a variety of intriguing surface features, including craters as
small as about 300 meters (about 300 yards) across.
This is one of a set of 68 NAC images showing landscapes near Mercury's
equator on the side of the planet never before imaged by spacecraft.
From such highly detailed close-ups, planetary geologists can study the
processes that have shaped Mercury's surface over the past 4 billion
years.
One of the highest and longest scarps (cliffs) yet seen on Mercury
curves from the top center down across the right side of this image.
(The Sun is shining low from the left, so the scarp casts a wide
shadow.) Great forces in Mercury's crust have thrust the terrain
occupying the left two-thirds of the picture up and over the terrain to
the right. An impact crater has subsequently destroyed a small part of
the scarp near the top of the image.
This image was taken from a distance of only 5,800 kilometers (3,600
miles) from surface of the planet and shows a region about 170
kilometers (about 100 miles) across.
Mercury's Cratered Surface
During its flyby of Mercury, the MESSENGER spacecraft acquired
high-resolution images of the planet's surface. This image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=120>,
taken by the Narrow Angle Camera (NAC) on the Mercury Dual Imaging
System (MDIS), was obtained on January 14, 2008, about 37 minutes after
MESSENGER's closest approach to the planet. The image reveals the
surface of Mercury at a resolution of about 360 meters/pixel (about
1,180 feet/pixel), and the width of the image is about 370 kilometers
(about 230 miles).
This image is the 98th in a set of 99 images that were taken in a
pattern of 9 rows and 11 columns to enable the creation of a large,
high-resolution mosaic of the northeast quarter of the region not seen
by Mariner 10. During the encounter with Mercury, the MDIS acquired
image sets for seven large mosaics with the NAC.
This image shows a previously unseen crater with distinctive bright rays
of ejected material extending radially outward from the crater's center.
A chain of craters nearby is also visible. Studying impact craters
provides insight into the history and composition of Mercury as well as
dynamical processes that occurred throughout our Solar System. The
MESSENGER Science Team has begun analyzing these high-resolution images
to unravel these fundamental questions.
------------------------------------------------------------------------
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a NASA-sponsored scientific investigation of the planet
Mercury and the first space mission designed to orbit the planet closest
to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and
after flybys of Earth, Venus, and Mercury will start a yearlong study of
its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie
Institution of Washington, leads the mission as principal investigator.
The Johns Hopkins University Applied Physics Laboratory built and
operates the MESSENGER spacecraft and manages this Discovery -class
mission for NASA.
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