. Landing into the Tycho crater

Apollo 12 - Pinpoint For Science (1970)

Credit: AIRBOYD

"Astronauts: Charles Conrad, Jr., Richard F. Gordon, and Alan L. Bean Launch date: November 14, 1969 Man's second journey to the Moon is for science. The first EVA includes setting up Apollo Lunar Surface Experiments Package (ALSEP) for the return of scientific data. The second EVA includes a geological traverse and the inspection of Surveyor 3, an unmanned spacecraft that landed on the Moon in 1967. A solar eclipse is recorded, findings to-date are summarized, and commentaries by noted scientists are included.

 
 

 
 

 

Impact melt

Central Peak

On 10 June 2011 the LRO spacecraft slewed 65 degrees to the west, allowing the LROC NACs to capture this dramatic sunrise view of Tycho crater.

TYCHO CRATER

Tycho has a diameter of 85 km and a depth of about 4.5 km. Located at 11.1° West and 43.4° South, Tycho is the youngest large crater on the nearside of the Moon with a conspicuous ray system. It is thought to have been absolutely dated, from a sample collected during Apollo 17 from the slope of the South Massif. 

An oblique view of Tycho crater looking from east-to-west. Image was acquired on 2 November 2014 from an altitude of 59 km. The central peak rises more than 2000 m above the crater floor and the far wall exhibits more than 4500 m of relief. Image: M1169552252LR

 
 

Tycho could potentially be a two-mission site. If it were deemed possible, a mission could also land inside Tycho to sample the floor, central peak, and or some of the crater‘s walls. At this point, it is unknown whether a mission to Tycho‘s floor is possible because of possible surface roughness. However, if possible we suggest a landing site at approximately 42.98° S, 10.78° W. The slope of this region is 3.66°. The landing location compared to our rim location, as well as a NAC image of the landing site, are shown in Figs. 7.56 and 7.57.

 
 

A POTENTIAL LANDING SITE TO STUDY A DIVERSITY OF REGOLITH PROCESSES AND SPACE WEATHERING  

A. Przepiórka and al. - 43rd Lunar and Planetary Science Conference (2012)

Tycho is a young Copernican age crater (~110 Ma [4]) with a diameter of ~85 km [4].  Continuous ejecta extends to a distance of ~110 km [5] beyond the crater rim and distinctive crater rays, visible from Earth, extend to distances of 2,000 km [4]. The suggested landing site is located at ~41.4° S and 11.8° W, which is ~20 km northwest of the Tycho crater rim. (see the red circle below)

The landing site is located on the continuous ejecta blanket of Tycho, ~20 km from the crater rim (Fig. 2). Ancient regolith may be exposed in layered depoits that are visible in the crater rim. Ranges of exploration are 10 km in radius, followed by 20 and 30 km.

This site is attractive for several reasons: it provides a sharp contrast between regolith formation on an impact melt-rich pond and on coarse, granular ejecta; between older highland regolith and young regolith of a suspected and easily verifiable age; between regolith for mation on units of different chemical and mineralogical compositions

Remote sensing maturity maps developed by Lucey et al. 2000b [7] suggest the landing site contains both very immature and intermediately mature soils, providing an opportunity to see the evolution of space weaterhing processes.  Furthermore, the Surveyor 7 spacecraft, which is ~20 km from the landing site, provides an opportunity to study the effects of space weathering on a known surface for a known amount of time (currently 44 yrs).

The Tycho landing site is not near a lunar magnetic anomaly, so all space weathering processes are expected to be normal and representative of the lunar highlands.  Solar wind production of volatiles can also be nicely calibrated here, because the exposure age (100 Ma) is known and the orbital relationship between the Moon and the Sun has not changed significantly over that period.

The chaotic floor into the Tycho crater has been formed by impact melt features

located on thick highlands crust south of Mare Nubium. The crater is 4 km deep and the central peak rises 2.4 km above the crater floor. The south-western section of its floor is 200 m higher than the rest, probably a result of greater slumping occurring along that section of the crater rim (Margot et al., 1999). Numerous hummocky massifs are irregularly dispersed along the crater floor. These features evolve into more discrete terraces approaching the crater rim and the crater wall is lined with large scarps (Schultz, 1975). Tycho‟s most striking features are the bright rays that extend for thousands of kilometers across the Moon. One of these rays is thought to intersect the Apollo 17 landing site, 2000 km away, where it may have triggered a landslide dated to be 100 Ma. This is the best age approximation for the Tycho-forming impact event.

Left rim of Tycho's crater

Right rim of Tycho's crater  

On 15 January 2012 the Lunar Reconnaissance Orbiter slewed 64.5 degrees to the east to capture this astonishing view of the floor and central peak of Tycho crater. In June of 2011, LRO captured a view looking to the west. 

 

Tycho crater is one of the most visible and important craters on the Moon due to its extensive, bright ray system. It appears in early geological maps of the Moon, for example in the map of the lunar nearside by Wilhelms and McCauley (1971), as well as a more detailed map of the Tycho area by Pohn [1972]. The latter used Lunar Orbiter V photographs, with a resolution of around 100 m, to define 14 different units in and around Tycho. Based on the same photographs, a detailed map of the distribution of impact melt around Tycho was also published by Morris et al. [2000]. The new geomorphological map (above) shows the interior of the crater in more detail than ever before. A higher resolution map of the impact melt deposits (below) in and around the crater was also made.

Geological maps are made as a tool for understanding and interpreting the formation and modification of rocks exposed at the surface of the Earth, other terrestrial planets, asteroids, and/or moons. The construction of geological maps on the Earth typically involves going into the field to make direct observations and measurements of the rocks of interest. For cases where the field area is difficult to access, remote sensing data is used as the basis for making the maps. In the case of the Moon or other planetary surfaces, geologists usually do not have rock samples that can be directly tied to specific geologic units, so they draw boundaries between different units using the appearance or morphology of the different materials. The result is a geomorphological map, from which scientists make geologic interpretations.

New geomorphological map of Tycho crater, with legend. The units include: Ccp – central peak; Ccfhh – crater floor (hummocky high); Ccfhl – crater floor (hummocky low); Ccfs – crater floor (smooth); Ccw – crater wall; Ps – polygonal structures; Mf – melt flows; Mp – melt pools; Cebc – continuous ejecta blanket [Krüger et al., 2016].

Melt pool (black) distribution at Tycho crater superposed on LROC WAC global mosaic and LRO LOLA topography data. The highest abundance of melt pools (now solidified rock) is on the northeastern part of the Tycho ejecta blanket, whereas the lowest abundance is to the southwest. The white arrow shows the implied direction of the Tycho impactor [Krüger et al., 2016].

Tycho crater is thought to have formed from an impactor that hit the surface at an angle, arriving from the southwest. The distribution of impact melt around Tycho crater supports this interpretation, as there are fewer pools of impact melt to the southwest, and many to the northeast (see image below), which would have been downrange of the impact trajectory. After it was ejected from the crater, impact melt accumulated into larger pools in areas where preexisting craters made sinks that could easily trap the melt (see ‘a’ image below), or where preexisting crater rims prevented melt from travelling farther from Tycho crater (see ‘b’ on the right-above image).

Maps such as these shape our understanding of how we can use impact crater deposits to learn about the cratering process. No humans witnessed the impact event that created Tycho crater some 100 million years ago, but we can use the deposits it left behind to recreate how it happened. Read the full story of how this new map of Tycho crater was created and the insights it has provided into the formation of the crater:

References & Sources: Krüger T., C. H. van der Bogert, and H. Hiesinger (2016). Geomorphologic mapping of the lunar crater Tycho and its impact melt deposits, Icarus, 273, 164–181, doi:10.1016/j.icarus.2016.02.018.