[meteorite-list] LRO Images Chang'e 3 Lander and Rover From Above

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 30 Dec 2013 15:59:07 -0800 (PST)
Message-ID: <201312302359.rBUNx7ub000202_at_zagami.jpl.nasa.gov>


Chang'e 3 Lander and Rover From Above
December 30, 2013

LROC NAC view of the Chang'e 3 lander (large arrow) and rover (small arrow)
just before sunset on their first day of lunar exploration. LROC NAC M1142582775R,
image width 576 m, north is up [NASA/GSFC/Arizona State University].

Chang'e 3 landed on Mare Imbrium (Sea of Rains) just east of a 450 m diameter
impact crater on 14 December 2013. Soon after landing, a small rover named
Yutu (or Jade Rabbit in English) was deployed and took its first tentative
drive onto the airless regolith. At the time of the landing LRO's orbit
was far from the landing site so images of the landing were not possible.
Ten days later on 24 December, LRO approached the landing site, and LROC
was able to acquire a series of six LROC Narrow Angle Camera (NAC) image
pairs during the next 36 hours (19 orbits). The highest resolution image
was possible when LRO was nearly overhead on 25 December 03:52:49 UT (24
December 22:52:49 EST). At this time LRO was at an altitude of ~150 km
above the site, and the pixel size was 150 cm.

LROC NAC before and after images of the Chang'e 3 landing site [NASA/GSFC/Arizona
State University].

The rover is only about 150 cm wide, yet it shows up in the NAC images
for two reasons: the solar panels are very effective at reflecting light
so the rover shows up as two bright pixels, and the Sun is setting thus
the rover casts a distinct shadow (as does the lander). Since the rover
is close to the size of a pixel, how can we be sure we are seeing the
rover and not a comparably sized boulder? Fortuitously, the NAC acquired
a "before" image (M1127248516R) of the landing site, with nearly identical
lighting, on 30 June 2013. By comparing the before and after landing
site images, the LROC team confirmed the position of the lander and rover,
and derived accurate map coordinates for the lander (44.1214?N, 340.4884?E,
-2640 meters elevation).

Chang'e 3 lander panorama [Images from CNSA; compiled by Di Lorenzo and
Kremer] showing Yutu shortly after it drove down the ramp to the surface.
Yellow lines connect craters seen in the panorama and the LROC image (taken
at a later date after the rover had moved), red lines indicate approximate
field of view of the panorama.

The lander set down about 60 meters east of the rim of a 450 meter diameter
impact crater (40 meters deep) on a thick deposit of volcanic materials.
A large scale wrinkle ridge (~100 km long, 10 km wide) cuts across the
area and was formed as tectonic stress caused the volcanic layers to buckle
and break along faults. Wrinkle ridges are common on the Moon, Mercury
and Mars.

LROC WAC context mosaic for the Chang'e 3 landing site (large white arrow);
small white arrows indicate wrinkle ridge and small black arrows delimit
boundary between "red" mare (northeast) and "blue" mare (southwest), image
is 100 km wide [NASA/GSFC/Arizona State University].

Lunar mare basalts are divided into two main spectral (color) types: "red"
and "blue" (blue is perhaps a misnomer, think "less red"). Basalts on
the Moon (same on Earth) are composed mainly of two minerals, pyroxene
and plagioclase, though olivine and ilmenite can sometimes occur in significant
amounts. The presence of ilmenite (FeTiO3) results in lower reflectance
and a "less-red" color - thus the blue basalts. The landing site is on
a blue mare (higher titanium) thought to be about 3.0 billion years old.
The boundary (black arrows in above WAC mosaic) with an older (3.5 billion
years) red mare is only 10 km to the north.

LROC WAC color (689 nm, 415 nm, 321 nm) overlain on WAC sunset BW image.
Note the proximity of the landing site to a contact between red and blue
maria [NASA/GSFC/Arizona State University].

A large area LROC WAC topography map of the Imbrium basin and surrounds
is available here.

LROC NAC before and after shown in the animation at the top of this Featured
Image [NASA/GSFC/Arizona State University].
Received on Mon 30 Dec 2013 06:59:07 PM PST

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