Steampunk Mars/ Cold War crossover

[marvin]

I was think of doing a GURPS Dying Mars/Space 1889 crossover with something like Red Storm Rising.

So the gist is that...

Ancient Artifact somehow transfers every other inner planet, Vulcan, Venus, Mars from a steam punk setting to a more modern year during the late Cold War. For simplicity's sake lets say 1973 (last year of Vietnam and a year after the last Apollo mission).

So my questions are...

How long would it take Earth to notice the difference? I'd imagine that would occur rather quickly.

How quickly could we send a manned mission to each of these planets?

Assuming a slightly modified Space 1889 setting for the Steampunk worlds; how would the Europeans on these planets fare until the Earth nations re-establish contact?

(NOTES: No Ether in space though I would be open to a sudden advancement in nuclear plasma propulsion.)

Thank you very much.
Benjamin