Saturday, June 06, 2009

Hubble Reveals Potential Titanium Oxide Deposits at Aristarchus and Schroter's Valley Rille

Credit: NASA, ESA, and J. Garvin (NASA/GSFC)Aristarchus Crater in False Color

This color composite focuses on the 26-mile-diameter (42-kilometer-diameter) Aristarchus impact crater, and employs ultraviolet- to visible-color-ratio information to accentuate differences that are potentially diagnostic of ilmenite- (i.e, titanium oxide) bearing materials as well as pyroclastic glasses. The symphony of color within the Aristarchus crater clearly shows a diversity of materials — anorthosite, basalt, and olivine. The images were acquired Aug. 21, 2005. The processing was accomplished by the Hubble Space Telescope Lunar Exploration Team at NASA's Goddard Space Flight Center, Northwestern University, and the Space Telescope Science Institute. False-color images were constructed using the red channel as 502/250 nanometers; the green as 502 nanometers; and the blue as 250/658 nanometers. North is at the top in the image.




Credit: NASA, ESA and J. Garvin (NASA/GSFC)
This view of the lunar impact crater Aristarchus and adjacent features (Herodotus crater, Schroter's Valley rille) illustrates the ultraviolet and visible wavelength characteristics of this geologically diverse region of the Moon. The two inset images illustrate one preliminary approach for isolating differences due to such effects as composition, soil maturity, mixing, and impact ejecta emplacement. The color composite in the lower right focuses on the 26-mile-diameter (42-kilometer-diameter) Aristarchus impact crater, and employs ultraviolet- to visible-color-ratio information to accentuate differences that are potentially diagnostic of ilmenite- (i.e, titanium oxide) bearing materials as well as pyroclastic glasses.

The same is the case for the image of a section of Schroter's Valley (rille) in the upper right. Bluer units in these spectral-ratio images suggest enrichment in opaque phases in a relative sense. The magenta color indicates dark mantle material which scientists believe contains titanium-bearing pyroclastic material.

The symphony of color within the Aristarchus crater clearly shows a diversity of materials — anorthosite, basalt, and olivine. The impact crater actually cut through a mare highlands boundary with superposed pyroclastics - a unique geologic setting on the Moon! The distinctive tongue of material extending out of the crater's southeastern rim is thought to be very olivine-rich material, based on Earth-based spectra and Clementine visible and infrared imaging data.

North is at the top in these images.

These images were acquired Aug. 21, 2005. The processing was accomplished by the Hubble Space Telescope Lunar Exploration Team at NASA's Goddard Space Flight Center, Northwestern University, and the Space Telescope Science Institute. False-color images were constructed using the red channel as 502/250 nanometers; the green as 502 nanometers; and the blue as 250/658 nanometers.



(Clementine, USGS slide 11)
Clementine color ratio composite image of Aristarchus Crater on the Moon. This 42 km diameter crater is located on the corner of the Aristarchus plateau, at 24 N, 47 W. Ejecta from the plateau is visible as the blue material at the upper left (northwest), while material excavated from the Oceanus Procellarum area is the reddish color to the lower right (southeast). The colors in this image can be used to ascertain compositional properties of the materials making up the deep strata of these two regions.


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APOLLO

The points of reference for the earth-moon measurement are the earth-based telescope—in this case, the 3.5 meter telescope at Apache Point, and in particular, the intersection of the telescope mount axes—and the small, suitcase-sized retroreflector array placed on the lunar surface by Apollo astronauts (pictured is the Apollo 11 reflector at Tranquility Base). A total of four lunar retroreflectors are functional: three Apollo reflectors from Apollo 11, 14, and 15 (three times bigger than 11 & 14), and one French-built, Soviet landed (unmanned) unit from the Luna 21 mission. A significant part of the challenge of lunar range modeling is converting this point-to-point measurement into a distance between the center-of-mass of the earth and the center-of-mass of the moon. It is only after this reduction that one can consider the interesting part of the problem: the dynamics of the earth-moon-sun system. For more general information on the technique, see this description of how the technique works and why we're performing this experiment.


Location of the reflector landing sites

APOLLO Laser First Light

Another picture from July 24, 2005. Larry Carey is seen standing on the catwalk performing aircraft spotting duties. Bruce Gillespie is the other spotter, hidden by the pine tree. On some viewing screens, the green beam may be barely visible leaving the dome. The beam is about as visible as the Milky Way. Part of Ursa Minor is at right, and Draco at upper left. Photo by Gretchen van Doren.


A picture from the August 2005 run by Gretchen van Doren, showing the laser beam making its way to the (over-exposed) moon. No, the moon is not exploding under the influence of our 2.3 Watt laser! The edge-brightening of the beam can be seen, as the telescope secondary mirror robs the beam of light in its center. Orion is seen at right.


A picture from the June 2006 run showing the back of the telescope, the APOLLO laser enclosure (left), the beam heading moon-ward, and the moon intself. The moon is actually a crescent, but so terrifically overexposed (16 seconds) that it looks rather round.


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Question 4 : What is the structure of Mercury's core?


Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

More recently, Earth-based radar observations of Mercury have also determined that at least a portion of the large metal core is still liquid to this day! Having at least a partially molten core means that a very small but detectable variation in the spin-rate of Mercury has a larger amplitude because of decoupling between the solid mantle and liquid core. Knowing that the core has not completely solidified, even as Mercury has cooled over billions of years since its formation, places important constraints on the thermal history, evolution, and core composition of the planet.




Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This MESSENGER image was taken from a distance of about 18,000 kilometers (11,000 miles) from the surface of Mercury, at 20:03 UTC, about 58 minutes after the closest approach point of the flyby. The region shown is about 500 kilometers (300 miles) across, and craters as small as 1 kilometer (0.6 mile) can be seen in this image.


The Gravity Field

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