Scientific Preparations for Lunar Exploration with the European Lunar Lander

Working schematic of the ESA Lunar Lander [Astrium].

James Carpenter, et al
ESA

Abstract - Recent Lunar missions and new scientific results in multiple disciplines have shown that working and operating in the complex lunar environment and exploiting the Moon as a platform for scientific research and further exploration poses major challenges. Underlying these challenges are fundamental scientific unknowns regarding the Moon’s surface, its environment, the effects of this environment and the availability of potential resources. The European Lunar Lander is a mission proposed by the European Space Agency to prepare for future exploration. The mission provides an opportunity to address some of these key unknowns and provide information of importance for future exploration activities.

Approach and Landing Profile The baseline design of the ESA Lunar Lander mission is unchanged since development began in 2010. In addition to real world testing and evaluation of robotic navigation, terminal descent and hazard avoidance, the array of on-board experiments and instruments eventually carried to the lunar surface in 2018 have continually been updated to match the growing knowledge base accumulated by an international fleet of spacecraft. The Carpenter study details the surface mission as projected in July 2012 [Astrium].

Areas of particular interest for investigation on the Lunar Lander include the integrated plasma, dust, charge and radiation environment and its effects, the properties of lunar dust and its physical effects on systems and physiological effects on humans, the availability, distribution and potential application of in situ resources for future exploration. A model payload has then been derived, taking these objectives to account and considering potential payloads proposed through a request for information, and the mission’s boundary conditions. While exploration preparation has driven the definition there is a significant synergy with investigations associated with fundamental scientific questions.

This paper discusses the scientific objectives for the ESA Lunar Lander Mission, which emphasize human exploration preparatory science and introduces the model scientific payload considered as part of the on-going mission studies, in advance of a formal instrument selection.

Download arXiv study 1207.4965.pdf

View from Vavilov

Vavilov (0.8°S, 138.8°W), the 'relatively recent' 98 km crater straddles a crossroads in the violent timeline of the Moon's history and sports some of the Moon's highest elevations on the northern and western rim. Interestingly, Vavilov formed nearly on top of a similarly sized and much older crater whose rim is still visible as a semicircle immediately northeast. Both craters carved out the same unique notch in the west wall of Hertzsprung impact basin. Image from 160 kilometer wide field of view cropped from a LROC Wide Angle Camera monochrome (566 nm) mosaic stitched from eight June 3, 2010 orbital viewing opportunities averaging 76 meters per pixel with an incidence angle of 64.5° from 55 km altitude [NASA/GSFC/Arizona State University].

WAC-derived elevation model (GLD100) Scene elevation (meters)
minimum = 2131.00, maximum = 9317.00 NASA/GSFC/Arizona State
University].

The elevation models of the Moon, built up during the record-breaking first 10,000 orbits by the Lunar Reconnaissance Orbiter (LRO), are finally allowing us to see the lunar surface in definitive detail. Naturally, this is especially true of the farside, invisible from Earth, and the polar regions. Even the vast highlands of the farside, unseen before 1959, have either been imaged at very wide angles or at low angle in part.

The Lunar Reconnaissance Orbiter Camera (LROC) in particular has been a spectacular success at imaging nearly half the Moon's surface at very high resolution and in surveying the entire Moon under a wide range of lighting conditions. One result is a highly accurate digital terrain model that just keeps getting better.

A weak attempt to represent a 100 degree wide panorama of the Vavilov interior and southern rim from its highest elevations situated along that crater's north rim. For the first time LROC is allowing us to imagine what that view might be, but it still does such a scene little justice to squeeze it into a 580 pixel-wide image [NASA/GSFC/ILIADS/Arizona State University].

Until LRO, many, but not all, of the wide angle views of the lunar farside have been focused on low resolution wavelength analysis, albedo, mineral and some low light relief. And even millions of laser altimetry measurements haven't matched the number of points recorded by LOLA during the LRO's present mission, already in lunar orbit far longer than any previous spacecraft. The record of the location of places photographed and measured hasn't been helped by the simple fact that no one really knew the Moon's actual shape and size with a high accuracy until Japan's Kaguya (SELENE-1) mission.

The Moon's highest elevations (10,761 meters) are now believed to be more than 600 km northwest of Vavilov, on the rounded wide rim of the crater Engel'gardt, but as we round the Moon's western rim, past Oceanus Procellarum and north of Mare Orientale where the farside highlands begin, and continue to proceed westward along the Moon equator the first very highest elevations encountered are on the north and western rim of Vavilov.

Easily among the highest elevations east of Engle'gardt East is on the upper reaches of the slumping wide north wall of Vavilov. We can only guess whether those heights could have once been much higher. The chaotic terraces of the western interior of Vavilov testify to a high degree of slumping, massive landslides underway since the crater formed. LROC WAC observation M130205287C (566 nm), orbit 4321, June 3, 2003; incidence 64.67° with a resolution of 77.11 meters per pixel, from an altitude of 55.31 km [NASA/GSFC/Arizona State University].

That Vavilov is deeply notched into the west-southwestern wall of the vast Hertzsprung impact basin is not something one can easily tell from Clementine (1994) albedo imagery, for example. So many craters with extended ray systems, like Jackson, overlap over the farside highlands, already bright for their relative lack of the mare-filled basins that dominate the nearside, that getting a gauge on elevations has remained elusive until the LRO mission. With the human eye alone its nearly impossible. But there is a reason why Vavilov is different, and higher, in one half than the other.

The west-southwest of Vavilov is not as stark a contrast in elevations as its north wall but the elevations are still respectable. The highest point along that rim is 9317 meters, among the Moon's highest places, and the high ejecta blanket, outside Hertzsprung on this side of the crater, tapers off less dramatically as well. The interior on the west side of Vavilov is more dramatically terraced, and this was probably not the original rim, its original circumference having collapsed, probably many times. The view seen in high detail in LROC Narrow Angle Camera (NAC) M151440688L shows a couple of kilometers-wide strip near this high elevation, and that along with other detailed images seem to show the process of slumping is still, slowly, underway. LROC WAC  observation imaged at the same opportunity, LRO WAC observation M151440362C, orbit 7451 February 4, 2011; incidence angle 51.43° at a resolution of 81.2 meters per pixel from 58.55 km [NASA/GSFC/Arizona State University].

The Vavilov impact event was not the first to carve out a place on the wall of Hertzsprung. The crater is offset just a little to the southwest from the crater, of almost identical size, that first made the notch and first interrupted the full circle of the 590 km-wide Hertzsprung impact basin. Vavilov's progenitor came close to erasing it's sister sometime after, and all that remains of the older crater is a semicircle like a cup handle attached to Vavilov's northeast.

The LROC WAC-derived Digital Elevation Model (GLD100) brings Vavilov out of the glare, in false color. The terrain was already on the rise from the southeast before the Hertzsprung or Korolov (further westward along the farside equator) because the formation of the Moon's oldest, deepest and largest known South Pole Aitken impact basin, further southeast may have help to lift the whole wider area along its perimeter here 4 billion years ago. The uplift of the third ring of mountains around Hertzspring rose still higher, first interrupted here by the arrival of Vavilov D. The area carries the deep scars and secondary craters of what some believe to be the most recent mare-filled basin-forming impact at Orientale, to the southeast. Vavilov probably formed after that event, superimposed on all those more ancient happenings. Vavilov is about seven kilometers deep, from its floor to the heights on its north and west rims [NASA/GSFC/DLR/Arizona State University].

The high western side of Vavilov perched on the southwestern outer ring of Hertzsprung and, on closer examination, the scaring and secondary crater chains radiant from the energetic impact that formed Mare Orientale, straddling the Moon's west limb and visible on edge from Earth. The most influential morphology that lifted this area is mostly invisible from Earth, the wide and deep 4 billion year old South Pole Aitken (SPA) basin at lower left. Orthographic projection over the intersection of the Moon's equator and its 240th meridian east [NASA/GSFC/DLR/Arizona State University].

Vavilov was unfavorable placed for the Apollo mapping cameras, and not well situated, nor a priority, for the Lunar Orbiter photography before Apollo. Other than the polar regions, this area of the Moon received less attention than most other areas until Clementine, and then from a low-resolution experimental remote sensing standpoint. LRO has changed that, however, and so much else. We now know that the view, and from the standpoint of science, the excavation performed by the Vavilov progenitor warrants more attention.

Even from orbit Vavilov must be spectacular.

Courtesy of the NASA ILIADS application, the LROC 100m WAC Global Mosaic draped over the LOLA 128 px DEM (v.2), the simulated "orbital view" of Vavilov from 65 km over the center of Hertzsprung basin.

"Biggest, deepest crater" an excavation of the hidden, ancient Moon

Image 1. This is elevation map covering the northeastern portion of South Pole-Aitken basin, including the Apollo Basin, made using laser altimetry data from Japan’s Kaguya lunar orbiter. The false colors indicate height; red represents highlands, and blue represents the lowest areas. Dashed circles mark the location of the main and inner ring of the Apollo basin. The dashed line marks the location of the topographic profile illustrated in Image 2 below [JAXA/NASA/GSFC]. Full-resolution copy

Bill Steigerwald
NASA GSFC

Shortly after the Moon formed, an asteroid smacked into its southern hemisphere and gouged out a truly enormous crater, the South Pole-Aitken basin, almost 2400 km across and more than 8 km deep.

"This is the biggest, deepest crater on the Moon -- an abyss that could engulf the United States from the East Coast through Texas," said Noah Petro of NASA Goddard Space Flight Center. The impact punched into the layers of the lunar crust, scattering material across the Moon and out into space. The tremendous heat of the impact also melted part of the floor of the crater, turning it into a sea of molten rock.

That was just an opening shot. Asteroid bombardment over billions of years has left the lunar surface pockmarked with craters of all sizes and covered with solidified lava, rubble, and dust. Glimpses of the original surface are rare, and views into the deep crust rarer still.

Fortunately a crater on the edge of the South Pole-Aitken basin may provide just such a view. The Apollo Basin was formed by the later impact of a smaller asteroid, but still measuring a respectable 480 kilometers across.

"It’s like going into your basement and digging a deeper hole," said Petro. "We believe the central part of the Apollo Basin may expose a portion of the Moon’s lower crust. If correct, this may be one of just a few places on the Moon where we have a view into the deep lunar crust, because it’s not covered by volcanic material as many other such deep areas are. Just as geologists can reconstruct Earth’s history by analyzing a cross-section of rock layers exposed by a canyon or a road cut, we can begin to understand the early lunar history by studying what’s being revealed in Apollo."

Petro presented his results Thursday during the 41st annual Lunar and Planetary Science Conference in The Woodlands, Texas.

Petro and his team made the discovery with the Moon Mineralogy Mapper (M3), a NASA instrument on board India’s Chandrayaan-1 lunar-orbiting spacecraft. Spectral analysis of images from the experiment revealed portions of the interior of Apollo have a similar composition to the impact melt in the South Pole-Aitken (SPA) basin.

Image 2: This is a graph of the elevation (in meters) from the rim of the South Pole-Aitken basin through the Apollo basin made using data from Japan’s Kaguya spacecraft. The endpoints (A and A’) are marked in Image 1 above [JAXA/NASA/GSFC]. Full-resolution copy

As you go deeper into the Moon, the crust contains minerals have greater amounts of iron. When the Moon first formed, it was largely molten. Minerals containing heavier elements, like iron, sank down toward the core, and minerals with lighter elements, like silicon, potassium, and sodium, migrated to the top, forming the original lunar crust.

"The asteroid that created the SPA basin probably carved through the crust and perhaps into the upper mantle. The impact melt that solidified to form the central floor of SPA would have been a mixture of all those layers. We expect to see that it has slightly more iron than the bottom of Apollo since it went deeper into the crust. This is what we found with M3. However, we also see that this area in Apollo has more iron than the surrounding lunar highlands, indicating Apollo has uncovered a layer of the lunar crust between what is typically seen on the surface and that in the deepest craters like SPA," said Petro.

The lower crust exposed by Apollo survived the impact that created SPA probably because it was on the edge of SPA, several hundred miles from where the impact occurred, according to Petro.

Both SPA and Apollo are estimated to be among the oldest lunar craters based on the large number of smaller craters superimposed on over them. As time passes, old craters get covered up with new ones, so a crater count provides a relative age; a crater riddled with additional craters is likely to be older than one that appears relatively clean, with fewer craters overlying it. As craters form, they break up the crust and form regolith, an outermost layer of broken up rock gardened in to fine submicron-sized dust.

Image 3: Three views of the Apollo Basin taken with NASA’s Moon Mineralogy Mapper instrument on board India’s Chandrayaan-1 spacecraft. The false-color image on the right reveals composition; the blues indicate surfaces that don't have as much iron in them (highlands crusts which are low in iron in blue); other colors (teals, yellows, and oranges) indicate more iron-bearing minerals [NASA/ISRO]. Full-resolution copy

Although the Apollo basin is ancient and covered with regolith it still gives a useful view of the lower crust because the smaller meteorite impacts that create most of the regolith don’t scatter material very far.

"Calculations of how the regolith forms indicate that at least 50 percent of the regolith is locally derived," said Petro. "So although what we’re seeing with M3 has been ground up it still mostly represents the lower crust."

It’s likely Earth wasn’t spared the same bombardment experienced by the Moon. Giant craters on other worlds across the solar system, including Mercury and Mars, indicate bombardment was widespread. On Earth, however, the record of these events was largely eroded away long ago. Crust is recycled by plate tectonics and weathered by wind and rain, erasing ancient impact basins and obvious craters.

"The Apollo and SPA basins give us a window into the earliest history of the Moon, and the Moon gives us a window into the violent youth of Earth," said Petro.

The research was funded by NASA’s Discovery program, which conducts lower-cost, highly focused planetary science investigations designed to enhance our understanding of the solar system. M3 was managed by the NASA Jet Propulsion Laboratory in Pasadena, CA. Petro's team includes researchers from NASA Goddard, the University of Maryland, College Park, Brown University, Providence, RI, Analytical Imaging and Geophysics, LLC, Boulder, CO, the University of Tennessee at Knoxville, DARPA in Arlington, VA and the Johns Hopkins University Applied Physics Laboratory in Laurel, MD.

NASA Ames releases short-list of LCROSS target crater candidates

Click on the image for a larger image. Credit: NASA/Ames Research Center

And then there were six...

Since long before the joint launch of LRO and LCROSS, in late June, amateur and professional observers alike have pondered where best to target the LCROSS Centaur upper stage with it's shepherding observational satellite following only 400 kilometers behind. Since shortly before the launch the time and date of the impact and which of the Moon's two polar regions have been widely published.

At approximately 1130 hrs, Coordinated Universal Time, on October 9, the exhausted LCROSS Centaur upper stage will slam into the Moon's southern hemisphere, inside the rim of one of that region's many abyssal, permanently shadowed craters. Now, following years of speculation, mission planners at NASA Ames Research Center have narrowed the candidates down to six, some without names.

Among them is, perhaps ironically, is Shoemaker, next to Faustini, both barely visible through a kind of pass; a break in the Near Side rim of the vast South Pole-Aitken Basin, most of which resides on the Moon's Far Side. Between the Moon's eroded, broken vertebrae, poorly explored massifs like Malapert, a flash of kinetic energy, common-enough on the Moon, will be the scene of the swiftest, most carefully and closely observed explosions in history.

And the nominees are...

LCROSS Candidate Impact Craters
Designation	Crater Name	Sun Mask	Eath Mask	Latitude	Longitude
SP A	Faustini	2.3	0.9	-87.2°	89°E
SP B	Shoemaker	3.5	-0.6	-88.5°	50°E
SP C	Cabeus	3.0	8.5	-85°	35.5°W
SP CB	Cabeus B	0.9	-0.5	-81.7°	54.5°W
SP CC	none	2.5	0.1	-83.5°	16°W
SP D	Hawworth	2.7	0.8	-87.4°	5°W
SP F	none	1.8	0.5	-82.3°	12°E
SP G	none	2.4	0.4	-84.3°	1°E