# How deep a crater could an impactor spacecraft cause on Mars?

What would the best way be to crash an impactor into Mars with greatest topological effect? And how deep a crater could it excavate?

Mars missions to date have been designed to approach the planet at low speed to land or enter orbit. How would a mission to hit it at maximum speed and mass be designed? Would a Krafft-Ehricke style gravity assist turnaround about Jupiter be the best way? What should the proportions of fuel to impact mass be in the launched payload? Does it matter whether the payload consists out of solid tungsten or a fusion bomb? Assume a single of today's launchers or a Saturn V at most.

The motivation could be to then land science probes in that fresh crater of the underworld of Mars, but that's not the issue here. Just how it could be done if it were assumed to be wished for as the next mission to Mars today.

## 2 Answers

It comes down to how much spacecraft you want to throw at it.

Newton tells us that a high speed impactor will be basically stopped by displacing it's own mass. (Although if what it hits is hard enough it may stop sooner.) Also, an object which is very long and thin may punch a hole but not have the energy to clear the rubble away adequately.

The bigger your spacecraft, the deeper the hole.

• I seem to remember a nice documentary video that showed a historical re-enactment where metal balls were being carefully dropped into sand to try to settle the question of what was more important, $mv$ or $mv^2$. (of course as we know now they are both equally important!) But where exactly did " Newton (tell) us that a high speed impactor will be basically stopped by displacing it's own mass."? Of course you may mean Newton's laws rather than his actual writings, but some supporting link or reference or citation would be really helpful. – uhoh Jul 4 '17 at 5:14
• It has been proposed. THOR would make a 30 foot deep hole with a 1200 kg impactor at 5.3 km/s. – Mark Adler Jul 4 '17 at 13:34

The largest possible rocket is something like a Delta V. So a roughly 10 ton payload going at Mach 10 or so would have 50 gj of energy. That's 5% of a WW2 A bomb.

So the crater would be less than 100x100 feet or so and it would not penetrate into deep layers of the crust. For that you would be better off sending multiple spacecraft to gradually drill deep over time. This would be a major logistical feat because drill heads would constantly melt or wear out at extreme depth.

• I think orbital mechanics, the gravity wells of Mars, the Sun and potentially Jupiter, change that by alot on the impact side, compared to the energies on the launch side you reason about. – LocalFluff Jul 4 '17 at 7:15
• I don't think a Delta V rocket exists – Jake Blocker Jul 4 '17 at 19:03