[meteorite-list] MESSENGER's Mercury Flyby Science Data Now Safely on Earth

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 18 Jan 2008 14:48:39 -0800 (PST)
Message-ID: <200801182248.OAA17792_at_zagami.jpl.nasa.gov>

http://messenger.jhuapl.edu/news_room/status_report_01_18_08.html

MESSENGER Mission News
January 18, 2008

MESSENGER's Mercury Flyby Science Data Now Safely on Earth

A day after its successful flyby of Mercury, the MESSENGER spacecraft
turned toward Earth on Tuesday and began downloading the 500 megabytes
of data that had been stored on the solid-state recorder during the
encounter. All of those data, including 1,213 images from the Mercury
Dual Imaging System (MDIS) cameras, have now been received by the
Science Operations Center at the Johns Hopkins University Applied
Physics Laboratory in Laurel, Md. Preliminary analysis of these data by
the MESSENGER Science Team has confirmed that all seven MESSENGER
instruments are healthy and operated as planned during the flyby.

As MESSENGER flew by the planet, it missed its targeted aim point by
only 8.25 kilometers (5.12 miles), affording the critical gravity assist
needed to continue on a course to become - in 2011 - the first
spacecraft ever to orbit Mercury. During this first encounter, the
payload successfully conducted a carefully orchestrated sequence of
observations designed to take full advantage of the geometry of the
flyby trajectory and to optimize the science return from each instrument.

In addition to images of the previously unseen portion of the planet's
surface, measurements were made that will contribute to the
characterization of all aspects of Mercury and its environment, from its
metallic core to the far reaches of its magnetosphere. "We have one
excited Science Team," says MESSENGER Project Manager, Peter D. Bedini,
of APL, "and their enthusiasm is contagious."

The analysis of these data is just beginning, but there are already
indications that new discoveries are at hand.

------------------------------------------------------------------------

Two New Images from MESSENGER Team Reveal Overview of Mercury and the
Planet's Cratering History

------------------------------------------------------------------------

Overview of Mercury as MESSENGER Approached

As MESSENGER neared Mercury on January 14, 2008, the spacecraft's Wide
Angle Camera on the Mercury Dual Imaging System (MDIS) took images of
the planet through each of its 11 filters. This image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=123>
of the planet's full crescent was taken using the seventh filter, in
light near the far-red end of the visible spectrum (750 nm). The image
shows portions of Mercury previously seen by Mariner 10, but when
Mariner 10 flew by the planet at each of its encounters the Sun was
nearly overhead.

For this MESSENGER flyby, in contrast, the Sun is shining obliquely on
regions near the day/night boundary (called the terminator) on the
right-hand side of the crescent, revealing the surface topography in
sharp relief. This image illustrates how MESSENGER, during its future
flybys and subsequent orbital mission, will teach us much about the
portion of Mercury already imaged by Mariner 10, and not just because of
its superior camera and close proximity to the planet. The solar
lighting geometry makes an enormous difference.

This picture provides a global context for the MDIS Narrow Angle Camera
(NAC) images taken while MESSENGER was inbound. For example, the NAC
image of the crater Vivaldi, released earlier this week
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?page=1&gallery_id=2&image_id=118>,
would fit as a small patch on the terminator just above the center of
the crescent. The already released image that includes the crater Sholem
Aleichem
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?page=1&gallery_id=2&image_id=122>
shows a part of Mercury near the top of the crescent. More NAC images
of the incoming crescent will be released in the future.

This image was taken about 80 minutes before closest approach from a
distance of about 27,000 kilometers (17,000 miles) and shows features as
small as 10 kilometers (6 miles).

Mercury's Complex Cratering History

On January 14, 2008, MESSENGER observed about half of the hemisphere not
seen by Mariner 10. These images
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=124>,
mosaicked together by the MESSENGER team, were taken by the Narrow Angle
Camera (NAC), part of the Mercury Dual Imaging System (MDIS) instrument,
about 20 minutes after MESSENGER's closest approach to Mercury (2:04 pm
EST), when the spacecraft was at a distance of about 5,000 kilometers
(about 3100 miles). The image shows features as small as 400 meters
(0.25 miles) in size and is about 370 kilometers (230 miles) across.

The image shows part of a large, fresh crater with secondary crater
chains located near Mercury's equator on the side of the planet newly
imaged by MESSENGER. Large, flat-floored craters often have terraced
rims from post-impact collapse of their newly formed walls. The hundreds
of secondary impactors that are excavated from the planet's surface by
the incoming object create long, linear crater chains radial to the main
crater. These chains, in addition to the rest of the ejecta blanket,
create the complicated, hilly terrain surrounding the primary crater. By
counting craters on the ejecta blanket that have formed since the impact
event, the age of the crater can be estimated. This count can then be
compared with a similar count for the crater floor to determine whether
any material has partially filled the crater since its formation. With
their large size and production of abundant secondary craters, these
flat-floored craters both illuminate and confound the study of the
geological history of Mercury.

------------------------------------------------------------------------

Additional information and features from MESSENGER's first flyby of
Mercury will be available online at
http://messenger.jhuapl.edu/mer_flyby1.html. Following the flyby, be
sure to check for the latest released images and science results!

------------------------------------------------------------------------

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.
Received on Fri 18 Jan 2008 05:48:39 PM PST