Leonard David's INSIDE OUTER SPACE

Chang’e-4 Moon lander and rover.
Credit: Chinese Academy of Sciences

If all remains on track, a new Chinese Moon mission, Chang’e‐4, will be launched in late 2018 to attempt the first farside landing in history, headed for the Von Kármán crater, within the South Pole‐Aitken (SPA) basin. The scientific instruments of China’s farside spacecraft, mounted on a lander and a rover, will analyze both surface and subsurface of this region.

The SPA basin on the farside of the Moon is the largest known impact structure in the solar system. It is the key area to answer several important questions about the Moon, including its internal structure and thermal evolution.

Secondary craters within the landing region of Chang’e-4 that are formed by the Antoniadi crater. (a) Great elliptic circle that linked the center of the Antoniadi crater to the selected Chang’E-4 landing site. The base image is from the global mosaic obtained by China’s Chang’e-2 mission. (b) Secondaries within the Chang’E-4 landing region that are delivered by the Antoniadi crater. White arrows mark the secondaries, and the yellow line is the possible trajectory of ejecta launched by Antoniadi. The location of this area is denoted as the white box in (a). The base image is obtained by Japan’s Kaguya lunar orbiter.
Credit: Jun Huang, et al.

Source craters

The Von Kármán crater is approximately 115 miles (186 kilometers) in diameter, lying in the northwestern SPA basin. The topography of the landing region is generally flat.

Secondary craters and ejecta materials have covered most of the mare unit and can be traced back to at least four source craters: Finsen, Von Kármán L, Von Kármán L’, and Antoniadi). Extensive sinuous ridges and troughs in the area are identified spatially related to Ba Jie crater.

Secondaries within the proposed Chang’e-4 landing region that are formed by the Von Karman L and Von Karman L’ craters. The two source craters are located to the south of the landing region. The great elliptic circles represent possible ballistic trajectories (blue lines) of impact ejecta from the source craters. (a) The NW – SE trending secondaries that are formed by the Von Karman L’ crater. (b) The NE–SW trending secondaries that are formed by the Von Karman L crater. Both the images are obtained by NASA’s Lunar Reconnaissance Orbiter Camera (LROC WAC) operated by Arizona State University.
Credit: Jun Huang, et al.

New paper

The Chang’e-4 mission has been addressed in a recent paper led by Jun Huang State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China.

The paper’s key points are that a detailed 3-D geological analysis of the nature and history of Von Kármán crater has been done; the region contains farside mare basalts affected by linear features and ejecta material from a wide range of surrounding craters; and a new geological analysis provides a framework for the Chang’e-4 mission to carry out on-the-spot exploration.

Relay satellite

Already in place for the upcoming mission is the Chinese relay satellite Queqiao. It will enable farside communications for the Chang’e-4 and future farside missions.

Credit: CNSA

Queqiao was successfully launched in May on a Long March 4C from the Xichang Satellite Launch Center. That relay spacecraft has successfully reached an Earth-Moon L2 halo orbit to support communications between Earth and the Moon’s farside.

Group shot…China’s Chang’e 3 lander and Yutu rover.
Credit: Chinese Academy of Sciences

Lander, rover instruments

Since both the lander and the rover were designed as a backup for the December 2013 Chang’e-3 mission – a lander carrying the Yutu rover — some of the science payloads on Chang’e-4 are similar, such as a landing camera, a terrain camera, a panorama camera on the lander and a visible/near infrared imaging spectrometer, along with two ground penetrating radars able to reveal the subsurface structure of the landing area.

Additional instruments on the lander a low-frequency radio spectrometer to perform joint space physics observations with the low-frequency radio spectrometer on the Queqiao relay satellite.

Also onboard is a German lunar neutron and radiation dose detector to explore the farside surface radioactive environment. In addition, a lunar microecosystem is included for astrobiology experiments and public outreach.

A new instrument on the rover is the Swedish neutral atom detector designed to study the interaction between the solar wind and lunar surface materials.

Mini-biosphere

According to the state-run Xinhua news agency, the probe will carry a tin containing seeds of potato and arabidopsis, a small flowering plant related to cabbage and mustard. It may also tote along silkworm eggs to conduct the first biological experiment on the Moon.

This “lunar mini biosphere” experiment was designed by 28 Chinese universities, led by southwest China’s Chongqing University, The cylindrical tin, made from special aluminum alloy materials, weighs roughly 7 pounds (3 kilograms).

The tin also contains water, a nutrient solution, and air. A tiny camera and data transmission system allows researchers to keep an eye on the seeds and see if they blossom on the Moon.

The paper – “Geological Characteristics of Von Kármán Crater, Northwestern South Pole-Aitken Basin: Chang’E-4 Landing Site Region” – has been published in the American Geophysical Union’s Journal of Geophysical Research: Planets.

It can be found here:

http://www.planetary.brown.edu/pdfs/5294.pdf

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