I'm trying to create plausible scenario under which we could colonize Venus.

Is it possible that Venus could be hit by a planetoid and the impact strips its atmosphere and makes it spin faster?

I'm ready to handwave the planetoid and why it changed the orbit. I'm just interested in whether the impact do what I expect. For example by hitting it with Pluto.

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    $\begingroup$ Welcome to Worldbuilding! I have suggested an edit to improve the formatting a bit. I do have a question- you mention colonization, are you expecting to have a breathable atmosphere? $\endgroup$
    – John Locke
    Commented Oct 9, 2018 at 20:22
  • $\begingroup$ This seems related to a question that was closed for being unclear. $\endgroup$
    – Rob Watts
    Commented Oct 9, 2018 at 20:23
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    $\begingroup$ Hello Arista, and welcome! Such an impact will necessarily transform Venus into a fiery ball of molten rock. In time it will cool down, form a solid crust, and it may become ready to receive the colonists; but this will be many millions of years later. $\endgroup$
    – AlexP
    Commented Oct 9, 2018 at 20:24
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    $\begingroup$ This link might help - en.wikipedia.org/wiki/Orders_of_magnitude_(energy)#Over_1024_J. The Earth has 2.1e29 J of rotational energy, and since Venus is close to the same size it will need somewhere in the neighborhood of 1e29 J of energy to get spinning the same speed. As AlexP said, an impact that large is not going to make Venus habitable very quickly. $\endgroup$
    – Rob Watts
    Commented Oct 9, 2018 at 20:54
  • $\begingroup$ An impact of that size will not be good for Earthlings either. There is certain to be some significant shrapnel that hits our planet. $\endgroup$ Commented Oct 9, 2018 at 20:55

1 Answer 1


Here is a really good reference on the pros and cons of methods to terraform Venus, with some strong physics and science behind them

How Do We Terraform Venus?

The part you are interested in, is perhaps

In contrast, increasing the speed of Venus’s rotation would require tremendous energy, not to mention a significant number of impactors that would have to cone from the outer solar System – mainly from the Kuiper Belt. In all of these cases, a large fleet of spaceships would be needed to haul the necessary material, and they would need to be equipped with advanced drive systems that could make the trip in a reasonable amount of time


And when it comes to removing Venus’ atmosphere, things are equally challenging. In 1994, James B. Pollack and Carl Sagan conducted calculations that indicated that an impactor measuring 700 km in diameter striking Venus at high velocity would less than a thousandth of the total atmosphere. What’s more, there would be diminishing returns as the atmosphere’s density decreases, which means thousands of giant impactors would be needed.

In addition, most of the ejected atmosphere would go into solar orbit near Venus, and – without further intervention – could be captured by Venus’s gravitational field and become part of the atmosphere once again. Removing atmospheric gas using space elevators would be difficult because the planet’s geostationary orbit lies an impractical distance above the surface, where removing using mass accelerators would be time-consuming and very expensive.

and even

It has also been suggested that Venus’ rotational velocity could be spun-up by either striking the surface with impactors or conducting close fly-bys using bodies larger than 96.5 km (60 miles) in diameter. There is also the suggestion of using using mass drivers and dynamic compression members to generate the rotational force needed to speed Venus up to the point where it experienced a day-night cycle identical to Earth’s (see above).

The last one is interesting, because it posits that you do not need to actually HIT Venus, just fly buy it with enough mass.

  • $\begingroup$ Just flying by is actually pretty good. When we consider the last part of this article that could be a reasonable way to spin venus $\endgroup$
    – user55267
    Commented Oct 10, 2018 at 8:42
  • $\begingroup$ @Jannis IF the earth stopped spinning suddenly, but the air didn't, then neither would the oceans. A one thousand mile per hour splash just covered all of the non-mountainous land mass around the equator. $\endgroup$ Commented Oct 10, 2018 at 16:12

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