I believe it might proceed like this
1960s-1970s - Sovies and Americans have established a manned base on the moon. Japan, the EU, and other countries are represented in space.
Space tourism becomes common for the gentry, and upper middle class.
Satellites are a dime a dozen, being launched into space every month or week it seems. World Wide information exchange (something similar if not the Internet) becomes available.
Some probes are sent to Venus, Mercury, Mars, and the moons of Jupiter, where Mars and Venus are confirmed to be dead, and Interest turns to The Jovian moons.
(Possibility, as ASB as it is: A foreign pathogen or organism is brought to Earth accidentally from the upper atmosphere.)
1970s-1980s - Bad Economic times spell an end for the space industry. Russia and America keep their lunar colonies up as scientific research centers, although those centers are like the International space station is today: saved by imports from Earth, be it human or rescource .
Space Tourism is halted, and the orbiting resorts are either left in space or shot down by missiles.
Satelites, however remain in orbit providing a base for the internet or an internet equivalent.
If microbial life was confirmed by previous missions to Europa, after the thought of bioweapons, no good or bad would come if us Terroans left the organisms on Europa alone, as it has few precious minerals or other rescources.
1990s - A Few more probes are sent into Space. A satelite orbiting the moon discovers the first protoplanets, which initially get people interested in space travel, but turn out to be logistically impossible.
by 2000, little is different from OTL: Aliens exist, protoplanets exist, and Space is still cold and distant.