Taurus Littrow Valley: Apollo 17 Landing Site | NASA's Lunar Reconnaissance Orbiter
The Apollo 17 astronauts landed in the Taurus Littrow Valley over fifty-three years ago. One of their key science goals was to collect impact melt from the Serenitatis basin rim so an age date for this important basin could be established. Before the samples were returned most lunar geologists believed this basin to be relatively old amongst all lunar basins. When the age dates came in from the Apollo 17 highland impact melt samples it appeared that the Serenitatis basin was younger than previously thought (3.86 billion years), nearly the same age as the mighty Imbrium basin (young in terms of lunar basins). Jack Schmitt and Gene Cernan sampled rocks from South and North Massifs and the Sculptured Hills, all three thought to be formed as part of the Serenitatis basin impact event.
The wisdom at the time was that the old relative age assignment of the Serenitatis basin derived from remotely sensed image data must be wrong. Perhaps the confidence of that interpretation was undermined by the relatively poor resolution of the then-existing orbital image data for much of the eastern portion of the nearside of the Moon.
The new Wide Angle Camera (WAC) global mosaic and Narrow Angle Camera (NAC) high resolution views are allowing scientists to reevaluate many previously held ideas with much clearer data. A new look at the area around the Serenitatis basin using the geologic rule of superposition (Spudis and coworkers, 2011) with the Lunar Reconnaissance Orbiter Camera (LROC) images resulted in a confident determination that the Sculptured Hills are actually far flung ejecta from the Imbrium basin, and not Serenitatis basin material. Littrow crater in turn was formed on the rim of Serenitatis basin. Thus the Sculptured Hills formed after the Serenitatis basin formed, likely as ejecta from the Imbrium basin impact event.
First, if the Sculptured Hills are really Imbrium ejecta it is possible (or even likely) that the Apollo 17 impact melts do not represent the formation age of the Serenitatis basin, but rather that of the Imbrium basin. If so, the evidence that there was a late cataclysm (a big short spike in impact events) just got a lot weaker. On the other hand, if those impact melts do indeed come form the Serenitatis formation event, the fact that Serenitatis is relatively old amongst lunar basins means the late cataclysm was even more compressed than previously thought. In fact, it would suggest that 13-25 of the larger basins all formed within a short period of 50 million years (short in geologic time). Either way, the new determination of the relative age of the Serenitatis basin results in a radical new evaluation of the sequence of events early in lunar history.
Reflecting back on the last human landing on the Moon, and the results of the Lunar Reconnaissance Orbiter (LRO) and other recent missions, we can see that the Apollo landings were a fantastic start to our exploration of the Moon. Many questions were answered from data and samples collected during the Apollo era. Since then, many new discoveries about the Moon have arrived, and more key science questions have appeared. The work begun by astronauts Schmitt and Cernan is now being extended by LRO in preparation for the next generation of lunar explorers. With the LROC data we can now map out the best places to search for outcrops of Serenitatis rock (especially impact melt) and obtain a confident age date for this key basin that in turn places many of the other large basins in their proper absolute age.
LRO has made a 3-D map of the Moon's surface at 100-meter resolution and 98.2% coverage (excluding polar areas in deep shadow), including 0.5-meter resolution images of Apollo landing sites.
LRO has been studying the Moon from up close since 2009, making it the longest-lived lunar orbiting mission ever. The orbiter has mapped the Moon’s surface and measured its temperature, composition, and radiation environment in unprecedented detail. Data from LRO enables NASA, and our international and commercial partners, to select locations on the lunar surface where spacecraft and astronauts can safely land. The orbiter is also helping NASA identify areas near the Moon’s South Pole with crucial resources like water and extended sunlight that provides power for equipment and supports exploration activities.
https://science.nasa.gov/mission/lro/
Text Credit: Mark Robinson
Release Date: Dec. 12, 2012
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