In a first of its kind achievement China successfully soft-landed a probe on the far side of the Moon Thursday, a giant milestone for the nation as it attempts to position itself as the leading space power. Launched December 7, the Chang’e 4 spacecraft (named after the ancient Chinese moon goddess) landed in the eight-mile-deep Von Carmen crater in the South Pole Aitken Basin after an 11-minute descent from a low orbit nine miles above the surface. The China National Space Administration reported the lander transmitted back the world’s first close range color image of what some people call “the dark side of the moon”. By the time you read this a specially designed rover will descend from the probe and roll onto the moon’s surface to begin transmitting pictures of its journey. Their explorer, a modified version of the original Yutu rover which landed in 2013 on the near side of the Moon, is solar-powered, and propelled by six wheels. It has been designed to last a minimum of three months on the Moon. Just for the record, the far side of the moon is the hemisphere that never faces Earth due to a locked tidal rotation effect. This surface is sometimes mistakenly referred to as the “dark side of the moon,” a term made unscientifically famous by Pink Floyd’s 1973 album, even though this side receives just as much sunlight as we do. We just cannot see any features there because it is always pointed away from us.
The touchdown location for Chang’e 4’s rover is recognized as the largest, oldest, and deepest basin mapped on the Moon. Thought to be an impact crater, it is roughly 1,500 miles in diameter, one of the largest known in our Solar System. First noticed by Russian orbiting probe images taken from Luna 3 in 1962, the true depth of the basin from laser altimeter readings on the Apollo 15 mission truly astonished astronomers prompting some to believe that whatever hit the Moon eons ago excavated vast amounts of mantle materials from great depths below the surface. It is hoped that this rock is still on the surface and can be examined. If Chang’e 4 can find and study some of this matter, it would get an unprecedented view into the Moon’s internal structure and origins. In the coming months the lander-probe is designed to perform a multitude of tasks, including:
1. To measure lunar surface temperature.
2. Determine the chemical compositions of lunar material.
3. Record the intensity of cosmic ray bombardment.
4. Growing silkworm larvae in a sealed container on the Moon.
The last task is quite interesting. Here, space traveling worms are housed in a 6 pound aluminum container along with some potatoes and a few Arabidopsis plant seeds. Combined with air, water, and a special nutrient solution, this tiny biosphere constitutes its own complete ecosystem, with the potato and Arabidopsis breathing out oxygen after taking in the carbon dioxide exhaled by the silkworms. It is hoped to test how much the moon’s extremely low gravity affects the growth of living organisms and the quality of the silk spun by the worms. To monitor progress, a real time video system is watching the experiment. Maybe we can all tune into this experiment.
There is other news. The United States New Horizons mission, the one that sent back stunning photographs of the Planet Pluto in 2015, released detailed images of the most distant world ever photographed, a trans-Neptunian object nicknamed Ultima Thule. Data from the New Year’s Day flyby showed the icy world as two connected snowballs – unlike anything ever seen before. Looking at the photograph, one can see how the gravitational joining of two masses may have led to “planet building” in the early days of our Solar System, 4.5 billion years ago. Because Ultima Thule is considered a cold Kuiper Belt object, it is believed to be the most primitive body ever seen it is thought that both connected bodies are planetesimal aggregates of much smaller building blocks.
Being so far from the Sun at 46 AU’s (1 AU = distance Earth – Sun) one may wonder where the New Horizons probe gets its power from. At this distance the Sun is only a very bright star and obviously solar panels cannot work with the feeble light available. The answer is a radioisotope thermoelectric generator that provides 200 Watts enough to power the circuitry within. Made from 24 pounds of plutonium, it is expected to last until 2030.
Being so far away, it takes 6 hours for the signals to arrive here for downloading. Coupled with a tiny transmitter, the information stream is very slow and will continue to arrive over the next several months, with much higher resolution images yet to come.