Title text: I WONDERED why he kept asking whether we thought the impact speed was too low.
On the day this comic was posted (September 30th 2016), the Rosetta mission ended with the final descent of Rosetta onto the comet 67P. Landing Rosetta on the comet gave the scientists (Ponytail, Megan and Hairy) a chance to collect extra data from very close to the comet, using the spacecraft's powerful sensors.
Cueball however assumed that the landing was a "kinetic impact" mission to deflect a comet that was on a collision course with Earth. A similar scenario (but using a nuclear weapon implanted inside of the asteroid to deflect it) was depicted in the 1998 film Armageddon, of which Cueball is apparently a fan. Armageddon is a high-throttle action movie, infamous among NASA employees for its incredibly liberal application of artistic license. IMDb has a list of factual inaccuracies.
In reality, at the time Rosetta landed, 67P was already leaving the inner solar system and was a long way past Earth. It will return to the inner solar system in around 5 years' time, but its orbit will not pass close to the Earth in any foreseeable time.
Also, as the title text hints, Rosetta's speed was only 90 cm per second relative to the surface at the moment of impact (or about 2 mph/3.25 km/h; the speed of a slow walk), while the comet was traveling at 14.39 km/s. Given that Rosetta only weighs a couple of tons (or six horses), and 67P weighs nearly 10 billion tons (or 22 billion horses), Rosetta's landing will have no actual measurable effect on the comet's momentum. Cueball however, thinking they were trying to deflect the comet, would have thought the impact speed would need to be higher.
Rosetta (and its lander, Philae) were previously the subject of the comics 1402: Harpoons and 1446: Landing, and were mentioned in 1461: Payloads, 1547: Solar System Questions and possibly 1621: Fixion.
- [A control room with Megan and Hairy sitting on stools in front of an opposite desk with computers. Hairy has his arms in the air. Ponytail is standing between them with Cueball, she is watching Megan and he is looking at Hairy.]
- Megan: Signal lost.
- Megan: Rosetta has impacted the comet.
- Ponytail: Good work everyone.
- Hairy: Woooo!
- [Zoom on Ponytail, still looking at Megan and Cueball who has turned towards Ponytail.]
- Cueball: So.
- Cueball: Do you think we deflected it?
- [Ponytail turns to Cueball as does Hairy who turns and looks away from his computer.]
- Ponytail: Huh?
- Cueball: Did we hit the comet hard enough to deflect it away from Earth?
- [In a frame-less panel Ponytail talks with Cueball.]
- Ponytail: That... Is that what you thought we were doing?
- Cueball: I just assumed...
- [Megan enters whispering in Ponytail's ear, holding a hand up to her mouth. Ponytail still looks at Cueball who raises his arms up in the air.]
- Megan: He's a huge Armageddon fan. Let him have this.
- Ponytail: Okay, fine.
- Ponytail: Yes! We did it! The Earth is saved!
- Cueball: Wooo!
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