let us assume Venus and Mars are just habitable for Humans
(like Venus rotate 24 hours (not 240 days) and Mars is more massive)
wat inpact on Cold War Space Programs ?
after the fist space probe discover that the planets are habitable
it change political decisions
in OTL as probe show Mars look more like Moon and Venus is a Hell
intrest for Manned fights to there wend to Zero
means the Moonrace is only first step in Space Race
who reach first the Planets will become major goal in Space Race
in U.S. Politican change goal to the planets
NASA start Post Saturn-V booster development
with 1000000 pound (453 metric tons) Payload
one proposal were Philip Bono ROMBUS (Reusable !)
see
http://www.astronautix.com/lvs/rombus.htm
ROMBUS can be used as mainhardware for Deep Space Mission
http://www.astronautix.com/craft/proelena.htm
http://www.astronautix.com/craft/proeimos.htm
even as intercontinental troop transporter or Passengers flights
http://www.astronautix.com/lvs/ithacus.htm
http://www.astronautix.com/lvs/pegvtovl.htm
with change goal in Space Race in 1964
the New Booster are ready around 1974
so the U.S. First Mars Mission can land on 4 juli 1976
a nice nice gift for 200 year celebration of USA ...
It's a very long way to Mars by rocket: I'd think we'd want to put rather more time learning how to keep a crew alive in space for a couple years [1], developing better methods of radiation protection, etc. before we'd be up to sending people to Mars. Also, the cost and reusability projections of the ROMBUS seem rather optimistic at best. Agreed that a Mars and Venus with native lifeforms would be a huge boost for the manned space program, but '76 seems a bit early for a manned landing. A crapload of landers, crawlers, orbiters, etc. seems likelier for the first decade or so. (Of course, if the orbiter detects Massive Martian Cities, all bets are off, and even the Orion project might get dusted off).
Bruce
[1] given present studies of the probable damage due to radiation on a long trip, it's quite possible Mars in '76 means dead Astonauts before they can get back.