Quite naturally - 1960s were the time when we discovered that Solar System is a pretty barren place. Mariner IV sent back pictures of craters on Mars - proving it couldn't have an atmosphere dense enough for people. Venera series probes proved at about same time that Venus surface was unsurvivable for anything we could recognise as "life". Stars are too far away. That was about it.
Many people don't get the origins of enthusiasm of first years of the space era, it wasn't because of politics, it was because there were real hope to find intelligent life in the Solar System itself - as crazy as it might sound now. And almost total surety of finding at least some form of complex, multicellular life. Disappointment when the real data came in, was massive. That's why space program went nowhere after Apollo, becoming a politicised clown show - by the time Apollo 11 landed, it was abundantly clear there wasn't much to see or do in the Solar System.
It was because there were real hope to find intelligent life in the Solar System itself - as crazy as it might sound now.
Yes. Von Braun wrote an otherwise realistic novel in which earth's explorers find intelligent life on Mars.[1] Heinlein wrote realistically of native intelligent life on Mars and Venus, with far more benign environments then they actually have. But once probes got there, we got to see how bleak they are.
There's a little hope for extrasolar planets, now that we can detect some of them.
[1] https://en.wikipedia.org/wiki/Project_Mars:_A_Technical_Tale
In 1965, Clarke, Asimov, and other science writers were at NASA watching the first images appear. "Craters. Duh, it's right next to the asteroid belt, of course it has craters. Not that any of us thought of it beforehand..."
Do you have a reference for that account? I hadn't heard it before, and it doesn't sounds quite right.
They certainly knew the Earth and Moon had craters, so proximity to the asteroid belt isn't required.
I suspect they thought the atmosphere on Mars was thicker and like Earth, where the high rate of erosion erases evidence.
Digging around through archive.org I found https://archive.org/details/sim_popular-astronomy_1944-05_52... from Popular Astronomy 1944
> The following extracts are taken from pp. 49 and 50:
> “The recent dominance of the meteoritic impact theory of crater origin makes timely a review of the oases-crater question of Mars. In this treatise, these conclusions have been pointed out:
> “I, Meteorite craters are known on the Earth and Moon; therefore, craters exist on Mars.
> “2. The circular oases on Mars are the size, shape, and number of comparable lunar craters.
> “3. Crater depressions form a natural reservoir, accounting for the intense vegetation in the Martian oases,
> “4. The random distribution of crater oases is apparent, indicating that the canal system was adapted to this haphazard arrangement.
The reviewer of the above points out
> “Why didn’t someone think of the crater theory sooner? The answer is simple. Someone did. Back in 1892, at Arequipa, Peru, W. H. Pickering not only discovered the small black spots on Mars, but he also recognized their similarity to the circlets on the Moon. Because lunar craters were then believed to be volcanic, Pickering may be forgiven for implying that the Martian craterets also were of volcanic origin.
We now know these crater oases were not real. My point is only that some people proposed meteoric craters on the Moon before the 1960s.
BTW, the SF of the pre-Mariner era does have volcanic craters on Mars, like https://archive.org/details/Amazing_Stories_v15n01_1941-01_c... and https://archive.org/details/Startling_Stories_v07n03_1942-05... .
I also found https://archive.org/details/exploringmars0000rich/page/150/m... saying in 1954 "no irregularities due to shadows have ever been observed along the terminator—the line dividing daylight from dark—such as would be produced by Martian craters." The author was an American astronomer and also a SF writer in the 1950s. By this we know astronomers were already considering there might be craters on Mars as there are on the Moon.
Yup. One early Arthur C Clarke story had plants growing natively on the Moon.