Taurus Littrow Oblique

An oblique perspective on the Taurus Littrow Valley and the landing site of Apollo 17 (20.1911°N, 30.7722°E) from more than 270 kilometers away. The granularity captured is remarkable testimony to the power of the LROC Narrow Angle Camera. LROC NAC frame M192703697R, orbit 13427, May 26, 2012; spacecraft and camera slewed 56.09° from nadir, resolution 2.79 meters, from a point 131.29 km over 20.01°N, 38.78°E [NASA/GSFC/Arizona State University].

Joel Raupe

Lunar Pioneer

The eleventh, and most recent, release of Lunar Reconnaissance Orbiter Camera (LROC) photography to the Planetary Data System (PDS) might have passed unnoticed. The spacecraft, after all, has been orbiting the Moon for more than three years, presently at more than 100 km, as it has since the beginning of 2012, and a year has passed since the spacecraft's dramatic 22 kilometer barnstorming passes over the surface in late 2011. 

The nominal mission orbiting altitude of 40 to 60 kilometers could not be sustained forever, though certainly none have come closer to mastering the Moon's 'lumpy' gravity well than LRO's flight directors.

Results from this mission-conserving, more apparently sedate higher-altitude phase in the LRO extended science mission would not very dramatic, still covering the same ground, over and over, presently from a greater distance. But, as all who regularly observe the Moon from Earth already know, the Moon never seems to present the same face twice, and it always seems to deliver up to patient, alert and modestly equipped observers a new face each and every time they pause to take a look. Remarkably, this axiom is proving as true for LRO in polar orbit as it is for Earth-bound observers 400,000 km away.

For the moment, 'barnstorming' has been left to the GRAIL twins. Together with LRO and the ingeniously recycled ARTEMIS probes, the feast of having five U.S. space vehicles in lunar orbit simultaneously cannot compete with Curiosity on Mars, or Dawn and its departure from Vesta for Ceres.  Even after four decades of near-neglect, as happened in the Apollo era, even hardened lunatic fanatic followers of LRO, quite naturally, have a more difficult time sustaining their sheer awe of the stunning, long overdue mission.

When properly scaled, the now-distinctive, albeit brief, trace of human activity on the floor of Taurus Littrow Valley is just barely visible at the center of this frame, pushed to 200 percent. Though the Apollo 17 lunar module descent stage cannot be seen, the darker material once just below the surface around that artifact, as well as the path to and from the ALSEP and LRV sites, turned over by the feet of Gene Cernan and Jack Schmitt nearly 40 years ago, is definitely a part of this landscape, photographed from an incredible distance last May [NASA/GSFC/Arizona State University].

Though the announcement of this eleventh PDS release seemed slightly delayed observations collected by LRO cameras from mid-March through mid-June was already available, right on time, through Arizona State University's LROC PDS interface. You had to have coordinates of a chose piece of the Moon's surface enumerated, longitude and latitude of its meets and bounds, unless patient or idle enough to scroll through sequential, lossy thumbnails.

Soon after the formal announcement, however, updated and detailed LROC NAC and WAC observation footprints became available to users of Google Earth, and as a layer on the web-based LROC QuickMap. The latter publication allowed the lay-public to experience something of the kind of serendipity only selected scientists experience when they comb through its latest pictures.

At around 30 percent full resolution, the breadth of Taurus Littrow can be seen, the rectangle tracing the outline of the narrow field of view shown at 100 percent resolution in the opening image, further above. Almost the entire area, the now-familiar landmarks, explored by Cernan and Schmitt can be seen. LROC NAC M192703697R [NASA/GSFC/Arizona State University].

Not long after these releases, every 90 days, someone who deserves a distinguished medal uploads to the Washington University (St. Louis) web-servers carefully updated Google Earth Keyhole Markup Language (KMZ) LRO-derived NAC and WAC footprint files. 

And though the lunar map available using Google Earth is increasingly outdated, after loading selected, updated KMZ files users can sift large areas of the lunar surface with LROC NAC and WAC observational fields of view embedded, and with an adjustable sliding time scale. It's a great way to get a quick look at areas available at high-resolution and during a particular phase of the mission, each with different illumination angles, especially any newly available observations of a particular area of personal interest.

Another demonstration of LROC NAC capabilities. The footprints, the 'fields of view.' of LROC NAC observations M192703697R and M192703697L, set up much as an imaginary passenger on board the Lunar Reconnaissance Orbiter might have seen the Target of Opportunity with the naked eye, in polar orbit 133 kilometers over a point on the Moon about 245 km east of the Apollo 17 landing site in Taurus Littrow Valley. Both field of view are well within the Apollo corridor, and the Apollo metric camera interferometry elevation model, integrated into the Google Earth virtual Moon [NASA/GSFC/USGS/JAXA/ASU].

It's also a way to allow the eye to "pick a crooked stick out from a pile of straight ones," because the occasional oblique observation shows up quite naturally as a highly elongated footprint that stands out sharply from the regular course of straight north-south footprints that follow the LRO polar orbit.

A highly-reduced copy of a 9240x7930 pixel mosaic of nearly the entirety of both the left and right frames of LROC NAC observation M192703697. Unfortunately, the original image file weighs in at around 66Mb, probably too hefty for most people's immediate resources. It's unfortunate because so very much spectacular detail and "knowledge to be gained," some of it important to our improving picture of lunar morphology, can be seen in the jaw-dropping original. You can, if you have the bandwidth, download the unofficial mosaic HERE [NASA/GSFC/Arizona State University].

Just a quick survey, one of many routes into the wealth of data that is still being swept-up by the LROC cameras, uncovered a new oblique observation of Taurus Littrow (sampled in this post).

Though the landing site of Apollo 17 has been explored at high-resolution by LRO many times, is readily identified through modest telescopes, and has even been surveyed by Hubble, even up close the Moon deliveres on a well-earned reputation for new glory with even simple changes in camera perspective, as most recently at even medium resolution from LRO last May.

Even the distinct trace of human activity, from December 1972, can be picked out, together with the enduring Sculptured Hills, the bright dusting of material blown off South Massif by the impact that formed distant Tycho, and so forth. But is this latest really a unique perspective, or the first time Taurus Littrow has been photographed from the east?

The full-resolution M192793697LR mosaic (warning: 66mg) may be available, HERE.

Certainly the last time Taurus Littrow was photographed from the east before the arrival of Apollo 17.  On December 11, 1972, after separating from Ron Evans and the Command Module America (visible at center), in their 12 orbit and just prior to final descent, Gene Cernan shot a short series of pictures of the destination from his left window of the lunar module Challenger. At full resolution, comparing AS17-147-22465 with the M192703697LR mosaic reveals how little the landscape has changed.

Not quite. But, though hand-held camera shots by Gene Cernan were captured from much closer and from lower altitude, the LROC NAC mosaic seen in miniature above, under similar lighting conditions, shows advances in photography in four decades, much of it a direct result of manned and unmanned space exploration.

In time, its possible that a small impact may have left behind a large enough trace to show when comparisons are made between the LROC NAC mosaic and frames from Apollo 17 Magazine 147. Its even possible, perhaps, that a change in perspective will eventually allow us to discover the final resting place of the Apollo 17 lunar module ascent stage itself, which was intentionally impacted near South Massif after being jettisoned, just before the last Apollo lunar mission broke orbit and returned to Earth.

Related Posts:
LRO LAMP sharpens Apollo surface helium data (July 17, 2012)
Toxicity of Lunar Dust (July 2, 2012)
39 Years (and counting) (December 14, 2011)
Just another crater? (December 13, 2011)
Apollo metric camera maps completed (November 21, 2011)
Too brief an expedition to a lobate scarp (August 24, 2010)
Moon geologically active, cooling and shrinking (August 19, 2010)
Return to Moon, Schmitt says, important for protection of liberty (June 17, 2010)
Dr. Jack Schmitt salutes LROC's Mark Robinson and the LRO
camera team at Arizona State (November 10, 2009)
Apollo 17 from 50 kilometers (October 28, 2009)

Tycho's flash-frozen inferno

Tycho in a full Sun, 'low phase' illumination, the crown jewel of a Full Moon on Earth has only its relative youth to distinguish it from many similarly-sized craters of similar origin. - LROC Wide Angle Camera (643 nm) mosaic from seven orbital passes (9061 - 9067) June 11, 2011. Arrow marks location of terraced pools of impact melt detailed below [NASA/GSFC/Arizona State University].

Joel Raupe
Lunar Pioneer, LLP

Hardly rare in scope or origin from similar craters all over the Moon, Tycho stands out like a bright star in the nearside southern Highlands because its bright rays radiate outward over the face of an entire Full Moon. Those rays make Tycho visible to the naked eye on Earth.

At a youthful 109 million years of age, relentless gardening by micrometerors has not yet smoothed the crater's reflective rougher edges, nor has a never-ending rain of charged particles, from the Sun and beyond, merged it's coloration into the background.Later impacts have not superimposed themselves or covered over the flash-frozen record of the mere minutes and hours following the explosive release of kinetic energy that created Tycho.

Tycho under 'high phase' illumination, at sunrise shows it's elevations in stark contrast, without the blinding albedo that tends to blur the immediate area of impact into the much broader area affected by that impact. LROC WAC mosaic, with longitude and latitude lines released by the LROC team last July. The impact melt detailed below, pooled just beyond the southeastern rim in this 130 kilometer-wide field of view, is much easier to see in the full-size original LROC image release, available HERE [NASA/GSFC/Arizona State University].

Among these finer details retained by Tycho are the pools of impact melt on the inner terraces and not far outside the crater's high rim, like the 'paved' pond Surveyor 7 nearly landed on in 1968, seen in the stark beauty of LROC Narrow Angle Camera observations.

The progenitor, the object that struck the lunar highlands and created Tycho threw up a lot of material in those first seconds afterward. Some of this material sped away at escape velocity, casually returning to the surface much later, if ever. Some sped away laterally as an immediate shock wave, carrying with it enough force to clip the tops of mountains on the south edge of Mare Serenitatis, knocking down the bright material of the Tortilla Flats in Taurus Littrow, sampled by Apollo 17 in 1972.

Some of the cloud scooped up by the blast hesitated above the area from where it was lifted and piled back down onto the surface outside the molten scar but most of the height where Tycho formed had to have been there before the explosion. We can tell this from the deep rutted channels carved into the highlands for hundreds of kilometers away from its center. The shape of the lunar surface around Tycho is not defined by what piled up but what remained after thousands of square kilometers of material were gouged away.

Tycho seems nested in a kind of plateau, though the evidence appears to show that this plateau was defined out of the highlands by the impact event that created Tycho. Great three and four kilometer-deep gullies appear to have been scooped out and away by the blast, better seen in this virtual 3D oblique view looking north over the outer southeastern rim of Tycho. LROC WAC (643 nm) mosaic as an overlay upon the Kaguya (SELENE-1) lunar digital elevation model in Google Earth [NASA/GSFC/USGS/JAXA/Arizona State University/Google].

The terraces on the inner walls of Tycho became a place for impact melt to pool and cool, so the terraces, by and large, were unlikely to have been formed by later slumping. We're left with a picture, immediately after the Tycho impact event, of a ragged scar, glowing hot in those first hours, from the central peak of deeper rock that rebounded in a heap (never higher than a crater's rim) to the very lip of the outer rim. It must have been a scene right out of Dante's Inferno.

LROC Wide Angle Camera (WAC) monochrome (643 nm) observation M119950214M, LRO Orbit 2810, February 4, 2010; resolution 66.12 meters per pixel, incidence angle 64.73° from 47.55 km. The yellow rectangle roughly outlines the field of view within the entire from of the LROC Narrow Angle Camera (NAC) frame from which scenes following originated [NASA/GSFC/Arizona State University].

Zooming in on these "Southeast Tycho" impact melt ponds, in the images above and following, note the fan of these ponds seem to flow downhill from a particularly ragged spot on the rim and apparently from further north channeled from an less distinct portion of the circumference of Tycho's rim. It's hard to imagine Tycho filled to the "brim" with molten rock, though the original melt was probably higher before it solidified to its present level. 

It's easier to imagine very hot material briefly pasted on the inside walls of Tycho sliding down to pool and form the ponds on the inner wall terraces. The ponds on the outside of Tycho are relatively sparse, but so is the slope acreage elevations outside the crater's interior. Before the anatomy of Tycho cooled and hardened some of the hottest melt was slung high seems to have collapsed like the opening rip of an ocean wave, which quickly froze, liquid rock that fossilized forty million years before the KT Boundary Extinction event brought an end to the Age of Dinosaurs here on Earth.

As impact melt briefly ran down the exterior side of the southeast brim of Tycho and pooled, coming to a halt in the cold vacuum of space long before 'finding its own level,' what appear as grooves formed by flowing molten material appear closer in to be shattered rock that instead merely aided molten transport. LROC NAC observation M150578086R, LRO Orbit 7324, January 25, 2011; resolution 71 centimeters per pixel, incidence angle 69.84° from 44.74 kilometers [NASA/GSFC/Arizona State University].

Full resolution view of the pond shore at the upper northeast in the image immediately above. The impact melt that ponded here briefly 109 million years ago was still hot enough for gas trapped within to heave bubbles to its surface. The flow at this juncture was arriving from all direction and the rounded surface tension elsewhere testifies to the lava-like viscosity of the pond [NASA/GSFC/Arizona State University].

A second full-resolution view from LROC NAC M150578086R shows where melt from the Tycho event briefly flowed down a huge, powerful fall at a high slope between ponds more than a thousand meters apart in elevation [NASA/GSFC/Arizona State University].

Tycho may be the same as many other craters on the Moon, but it's relative youth "in Moon years" makes it an easy choice for mapping the immediate aftermath of a powerful impact on an airless body, at least for the next half billion years or so.

Related Posts:
Tycho Peak Spectacular!
Chaotic crater floor in Tycho
Polygonal fractures on Tycho ejecta
Impact melt on Tycho floor
Ejecta on Tycho floor