You beat me to it, Pauligirl.
The OP's linked story has a gaping hole in it - namely the historical context
In the early '70s the Soviet space program was reeling. By the time they had their spacecraft intended for manned circum-lunar missions (Zond)
debugged, the Americans had already made manned landings. The Soviet manned landing program was in shambles. Although they successfully flew their
LK lunar lander in Earth orbit (a mission equivalent to the US flight of Apollo 5), they could not get their massive and complex N1 rocket to fly
Part of the problem with the Soviet space effort was that they had several different programs competing for funding. In addition to the two
aforementioned manned-lunar programs, they also had two unmanned lunar programs, (the "Lunokhod" rovers and the sample-return missions) and two
manned space-station programs (Salyut and its secret military counterpart, Almaz), not to mention two high-profile interplanetary programs (Venera,
which ultimately succeeded and Mars, which did not).
When it became obvious that Apollo was a success, the Soviet propaganda machine announced that the USSR never intended
to land men on the Moon,
preferring instead to use unmanned probes for exploration while concentrating their manned effort on Earth-orbital "Salyut" space stations.
Gullible western media swallowed this lie hook, line & sinker.
After a rocky start (which included the highly publicized crash of Luna-15 while Apollo 11 was still on the lunar surface), the Soviets successfully
landed a rover and completed its first robotic sample return mission in 1970 (while Apollo was grounded following the near-disaster of Apollo 13).
Another rover landed in 1973 and two more sample return missions succeeded in 1972 and 1976 (The total weight of lunar material returned by these
three missions was roughly half-a-pound, recovered from wherever the probe happened to land. This is in stark contrast to the 800+ pounds of rock &
soil samples carefully documented & collected by the Apollo missions).
The Salyut program got off the ground in 1971. In June, the crew of Soyuz 11 docked with the world's first manned space station and spent 3 weeks
there - setting a new spaceflight endurance record. But triumph turned to tragedy when their Soyuz capsule depressurized as they were returning to
Earth, killing all aboard. Their next station, "Salyut 2" (actually an Almaz station) launched in 1973, but failed before the first crew could
arrive. Months later, the entire Soviet space station effort was upstaged by the spectacular US "Skylab" station, which was much larger and allowed
new manned space records to be set.
This brings us back to the OP:
The Soviets needed a win - very, very badly
. If they could have discovered evidence of extraterrestrial life from their cheap probes -
evidence that the expensive American program failed to uncover - then the boost to Soviet prestige would be incalculable, and the humiliation to the
"successful" Americans would be total. That they made no such announcement makes a crushingly-strong argument that no such discovery was made.
So what is that circular thing in the OP's linked article? Well that's easy
: It's a "zap-pit". Both the Americans & Soviets (and
scientists from all over the world who studied the returned lunar material) found them all over the samples.
Have you ever hit a rock with a hammer? If you do, and examine the broken material, you will notice that there are a lot more smaller pieces than
large ones. In fact, the smaller the fragment, the more of them there are. Similarly, out in space there are a lot more small bits of debris left
over from the formation of the solar system than there are large ones. Some are as small as the particles found in cigarette smoke. Our atmosphere
shields us from these high-speed flecks. When we see a "shooting star", the actual meteor is typically around the size of a grain of sand.
Our moon does not have an effective atmosphere that can stop meteors of any
size. They all - down to the smallest dust-mote - hit the ground
at several miles per second. Note that when I say "ground", I may be referring to a rock on the surface or even an individual particle of dirt.
When a smoke-sized dust-dot hits a dirt-speck at that speed, you still get an explosion - albeit a very small one (take THAT, Whoville!) that leaves a
crater that geologists whimsically called "zap-pits".
Here is another picture of one:
They can come in any size, with the upper limit being whatever it takes to shatter the target rock/particle.
Hope this helps.