I found myself wondering about what ever had happened to the Mariner 2 spacecraft (the first successful flyby of any planet) after it flew by planet Venus.

According to apesinspace.co it "continued in a heliocentric orbit." and that's all I can find.

So what actually happened to it?

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Rory Alsop
    Sep 22, 2022 at 17:42

1 Answer 1


After the close encounter with Venus on December 14, 1962, the last radio contact was on January 3, 1963.
No tracking can be done after that as the spacecraft is too small and too far away.

The Mariner 2 project report gives the orbital parameters of the heliocentric orbit after the encounter. (page 69).

Perihelion 105 415 000 km, aphelion: 183 423 000 km

If we extend that orbit into the future, we get new close encounters with Venus within a distance ~2.5 million kilometres after 10 and 12 years. Potentially one at just 0.14 million kilometres after 23 years, if the orbital parameters stay the same.

But the orbital parameters aren't going to stay the same. After each new encounter with Venus, which by this time there has been several of, the error in the measurements grow exponentially. It is a butterfly effect were the new orbit after an encounter is very sensitive to uncertainty in the initial orbit.

So nobody knows, and nobody can know, were Mariner 2 is now, other than that it is orbiting the Sun with a period slightly below a year.

  • 3
    $\begingroup$ The Horizons trajectory data for Mariner 2 stops at 1963-Jan-01, but even that "is intended for general historical purposes, but should be used cautiously for high-precision applications". ssd.jpl.nasa.gov/api/… $\endgroup$
    – PM 2Ring
    Sep 23, 2022 at 1:02
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    $\begingroup$ There was a simulation of the possible long-term behaviors of the Tesla in the space. As far I can remember, the result was a chaotic oscillation between the orbits of the Venus, Earth and Mars, with a likely collision with any of the bodies in some million years. (What also makes likely numerous close encounters, but without a collision.) I think, the fate of the Mariner2 will be the same. $\endgroup$
    – peterh
    Sep 23, 2022 at 9:35
  • $\begingroup$ @peterh Horizons can't do those long-term predictions, but it has ephemerides for the Tesla Roadster until 2090-Jan-2, and the body data page has extensive info ssd.jpl.nasa.gov/api/… "NOTE: long-term predictions Over time, trajectory prediction errors could increase more rapidly than the formal statistics indicate due to unmodeled thermal re-radiation or outgassing accelerations that are not currently characterized but may exist." $\endgroup$
    – PM 2Ring
    Sep 24, 2022 at 10:53

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