I love photos of the Earth from space. When they include the far side of the moon in the same frame, it only adds a little more of awesome. While we’ve heard little news of late about China’s Chang’e 4 mission to the lunar far side, these mission-related photos recently popped up online. They were taken from the Longjiang-2, one of two microsatellites launched to the moon last year to lay the groundwork for the Jan. 3 soft landing on the far side of the moon.
The still photo was taken on at 9:20 p.m. on Feb. 3 and reveals both a full Earth and a full moon. Only the full moon in this instance is happening on the lunar far side. On that same date, the moon was in new phase as seen from Earth. During new moon phase, the earth-facing half of the moon is completely dark because it appears in the same direction as the sun in the sky. No sunlight can touch it. We can’t see a new moon except in silhouette against the sun during a solar eclipse. Meanwhile, the far side basks in the heat of the day.
1.5-hour time-lapse of the moon (far side shown here) uncovering the Earth taken by China’s Longjiang-2 relay satellite on Oct. 7, 2018
If the poor resolution surprises you, it’s because it was snapped with a simple webcam that was made by students from the Chinese Harbin Institute of Technology. It’s connected to a little antenna which beams the file (only 16 KB in size) down to the Dwingeloo radio telescope in the Netherlands. Because the relatively weak signal has to travel a long distance, a large radio dish is needed to scoop it up. The volunteers that run the observatory helped with the downloading, which took 20 minutes for this image.
Meanwhile, NASA’s Lunar Reconnaissance Orbiter (LRO)was looking the other direction on Jan. 31 — back at the moon — when it took this spectacular photo of the Chang’e 4 landing site. The Yutu-2 rover and lander are only a few pixels across but you can see them both and their shadows cast in Von Kármán crater. The crater floor is covered by eruptions of basaltic lava similar to what pours out of Hawaii’s volcanoes. Chang’e 4 is still operational — both rover and lander survived the recent 2-week-long lunar night when temperature can drop to –280° F (–173° C) — and continues taking measurement of the composition of the lunar rocks.
Scientists are eager to know if the ancient farside lavas differ from those sampled on the near side. One thing we can say for sure is that the far side was pounded by asteroids and meteorites. Just look around: it’s craters as far as the eye can see.
Some are fresher than others but so many impacts have occurred here that the surface has been churned into powder and rock fragments called the lunar regolith. One of the telltale signs of a lunar meteorite, a fragment of the moon blasted out by an impact that later landed on Earth, is its texture. Most are made of thousands of smaller fragments welded together into a rock.