Lunar Crater Cornucopia And A Glimpse Of The Far Side

The richly-cratered lunar highlands are in view tonight. The terminator — where the sun is rising over the lunar surface — curves up along the left side of the moon.  Luc Viatour /

Like a middle-aged couch potato the moon’s been developing a paunch, leaving behind its delicate crescent figure and swells into a bulgy 8-day orb. Ah, but there’s beauty in that bulge. It’s filled with thousands of large, overlapping craters many of which you can see in a pair of binoculars magnifying from 7x to 10x. Just point, focus and marvel.

The top half of the moon displays fewer craters but more lunar seas or “maria” (MAH-ree-uh). These large, dark splotches are actually basins excavated by good-sized asteroids that filled with magma from below 3-3.5 billion years ago. The white areas of the moon, called the highlands, compose the original crust that formed nearly 4.5 billion years when the mostly-molten moon began to cool. It bears the record of billions of years of impacts by meteoroids of all sizes. That’s what’s on display tonight through Thursday.

Get your binoculars out tonight and take a look at the moon. Now is the best time to see craters with only a little bit of magnification. This simulation shows the moon tonight, June 10. Virtual Moon Atlas

You can see this battering in binoculars best right now. There are two reasons why. A large section of the highlands faces us squarely at the same time the sun is rising there. The low sun angle makes every crater, craterlet, mountain and cliff cast long shadows that to create a dramatic moonscape of shadow and light. The view in a small telescope will blow your socks off. Closer to full moon, the sun shines on the same craters but at a much higher angle. Shadows are so short, there’s little contrast between high and low spots, so everything looks flat and pasty. Lunar sunrise and sunset are the best times to view surface detail on the moon.

So keep an eye on the terminator — that’s the expanding curve along the left (eastern) side of the moon. During the moon’s waxing phases it marks the line of lunar sunrise. After full moon, the terminator defines the line of advancing sunset.

The Chinese rover and lander landed in the 115-mile-wide (186 km) crater Von Kármán on the moon’s far side. The crater is located near the South Pole-Aitken Basin, site of an enormous impact. China’s Chang’e 5 mission lunar sample return mission will launch later this year. NASA / LRO

Meanwhile, on the far side of the the Chinese Chang’e 4 lander and Yutu-2 rover are preparing for another long lunar night. Nights last about two weeks and get very cold — the rover has recorded temperatures as low as –310° F (–190° C). News of the mission comes in dribs and drabs, so there’s been little about its progress since May 28. At that time, the equipment had made it through five lunar nights since landing in the farside Von Kármán crater on Jan. 3, 2019 and was ready to begin its 6th lunar day. Future updates can be found at #ChangE4.

Part of a 360° panorama showing the Yutu-2 rover taken by the Chang’e 4 lander. CNSA
The rover makes tracks in the lunar soil — called regolith — with the lander visible at upper left. CLEP/CNSA

The crater lies within the South Pole-Aitken Basin, the largest, deepest and oldest impact basin on the moon and one of the biggest in the solar system. SP-AB is about 1,600 miles (2,500 km) across and 8.1 miles (13 km) deep and one of the best places on the moon to sample rocks from the lunar mantle, the deep layer of rock that lies beneath the crust. None of the Apollo missions collected mantle material, but the Yutu-2 rover identified rocks earlier this year with a composition different from the crust. Light reflected from the minerals revealed signs of olivine and pyroxene, materials expected to compose the mantle. As of late April, the Yutu-2 rover had traveled 587 feet (179 meters) from the lander.

This is a photo of the far side when it’s in full moon phase. The South Pole-Aitken Basin is the big, dark patch at the bottom. NASA/Goddard Space Flight Center Scientific Visualization Studio

Lunar phases on the near side and far side are complimentary. When we see a new moon, the far side is full. When we see a half-moon in the evening sky, the opposite half of the far side is lit up. And when we see a full moon, the far side is in new moon phase. Since the lander-rover lie along the mid-point of the lunar far side, the sun sets there about the same time we see a half-moon. Tonight, the moon will be 8-days-old with the rover and lander sliding into shadow at the start of the next long lunar night. Like two bears, they’ll remain in hibernation before waking up two weeks hence to start another day.

11 Responses

  1. kevan hubbard

    Have you ever seen any transient lunar phenomenon?just been reading about it over the last few weeks as Spock would have said “most fascinating.”hopefully this new lunar telescope in Spain will provide some answers.the fact that Collins aspied it from space would suggest that the phenomenon is genuinely on the Moon,well some of it, and not in between Earth and the Moon.

    1. astrobob

      I’ve never seen anything of that nature, Kevan. Most of those have been disproved as tricks of lighting, satellite flares, atmospheric conditions or overactive imaginations, but a few might be real. It’s certainly possible to witness a flash (especially if you’re in lunar orbit) from an impacting meteoroid — I believe 400+ flashes from impacts have been recorded on ground video cameras and at least one with the naked eye. As far as something native to the moon, I’m not aware of anything proven. Collins’ sighting is interesting but doesn’t validate TLPs one way or another — it was only an impression.

      1. kevan hubbard

        Non the less it’s got me moongazing a lot more!the modem popularizing of t.l.p.seems to originate with the late English astronomer Patrick Moore,he was a no nonsense kind of fellow.i think that Moore had seen t.l.p.hence his interest.outgasing of stuff in the Moon is another option.its raining now so I can’t look at the Moon tonight but did yesterday.

        1. astrobob

          Yeah, he was a smart dude. I tend to be skeptical because I’ve observed the moon a lot over the years and have never seen the slightest hint of a TLP. Again, for it to be visible in amateur scopes like Moore used it would have to cover a vast area something on the order of a kilometer or larger unless it were an outburst in the unlit area of the moon in which case a flash would almost certainly indicate a meteoroid impact. I’m happy though if it inspires lunar observation and perhaps one day proof-positive of a TLP.

          1. kevan hubbard

            It’s got me looking!I always resented the Moon because it flushed out the DSO’s but not so much now.this new German telescope which is in Spain, I’d guess because of the weather being clearer than Germany?,will be looking at the tlp phenomenon, Aristarchus seems to be the home of the majority of tlp as over the terminator line a few days ago when I looked at the daylight Moon (I was actually looking for seals and saw over 60 in 2 groups the Moon was a bonus!).

        1. astrobob

          Hi Carol,
          I do — absolutely. But the chances of someone seeing it randomly are very small. Most lunar seismic activity isn’t caused by volcanism but by the stress and strain of tidal interactions with the Earth. It would also have to be on a rather large scale to see volcanic-style outgassing visually except under certain conditions (say, outgassing near the terminator in low sunlight).

        2. kevan hubbard

          An idea I had and I must confess I don’t know enough about such matters is the solar wind interacting with radioactive elements on the Moon creating a natural fission reactor?a bit like the one in Gabon or it might be one of the other g countries in West Africa.the one in Africa is caused by decaying uranium.

    1. astrobob

      This was disproven some time back and described in an excellent article in Sky & Telescope magazine. Wish I could recall the issue.

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