In Part I of the series we saw how dark matter could cause mass extinction by inducing biosphere-wide cancer, stirring up volcanoes, or launching comets from the Oort cloud. In this second and final part, we explore its other options for maleficence.
World-devouring dark matter
The dark matter wind that we encountered in Part I has yet another trick to bring the show on this watery orb to an abrupt stop. As J. F. Acevedo, J. Bramante, A. Goodman, J. Kopp, and T. Opferkuch put it in their abstract, “Dark matter can be captured by celestial objects and accumulate at their centers, forming a core of dark matter that can collapse to a small black hole, provided that the annihilation rate is small or zero. If the nascent black hole is big enough, it will grow to consume the star or planet.” Before you go looking for the user guide to an Einstein-Rosen bridge, we draw your attention to their main text: “As, evidently, neither the Sun nor the Earth has suffered this fate yet, we will be able to set limits on dark matter properties.” For once we are more excited about limits than discovery prospects.
R-rated dark matter
Enough about destructions of life en masse. Let us turn to selective executions.
“Macro dark matter” is the idea that dark matter comprises not of elementary particles but composite objects that weigh anywhere between micrograms and tonnes, and scatter on nuclei with macroscopic geometric cross sections. As per J. J. Sidhu, R. J. Scherrer and G. Starkman, since the dark wind blows at around 300 km/s, a dark macro encountering a human body would produce something akin to gunshot or a meteor strike, only more gruesome. Using 10 years of data on the well-monitored human population in the US, Canada and Western Europe, and assuming that it takes at least 100 J of energy deposition to cause significant bodily damage, they derive limits on dark matter cross sections and masses shown in the adjoining figure.
We’re afraid there’s nothing much you can do about a macro with your name on it.
Inciteful dark matter
Dark matter could sometimes kill despite no interactions with the Standard Model beyond gravity. [Movie spoilers ahead.] In the film Dark Matter, a cosmology graduate student is discouraged from pursuing research on the titular topic by his advisor, who in the end rejects his dissertation. His graduation and Nobel Prize dreams thwarted, and confidante Meryl Streep’s constant empathy forgotten, the student ends up putting a bullet in the advisor and himself (yes, in that order). Senior MOND advocates, take note.
Vital dark matter
Lest we suspect by now that dark matter has a hotline to the Grim Reaper’s office, D. Hooper and J. H. Steffen clarify that it could in fact breathe life into desolate pebbles in the void. Without dark matter, rocky planets on remote orbits, or rogue planets ejected from their star system, are expected to be cold and inhospitable. But in galactic regions where dark matter populations are high, it could capture in such planets, self-annihilate, and warm them from the inside to temperatures that liquefy water, paving the way for life to “emerge, evolve, and survive“. The fires of this mechanism would blaze on long after main sequence stars cease to shine!
And perhaps one day these creatures may use the very DNA they got from dark matter to detect it.
 Dark Matter, Destroyer of Worlds: Neutrino, Thermal, and Existential Signatures from Black Holes in the Sun and Earth, J. F. Acevedo, J. Bramante, A. Goodman, J. Kopp, and T. Opferkuch, arXiv: 2012.09176 [hep-ph]
 Death and serious injury from dark matter, J. J. Sidhu, R. J. Scherrer and G. Starkman, Phys. Lett. B 803 (2020) 135300
 Dark Matter and The Habitability of Planets, D Hooper & J. H. Steffen, JCAP 07 (2012) 046
 New Dark Matter Detectors using DNA or RNA for Nanometer Tracking, A. Drukier, K. Freese, A. Lopez, D. Spergel, C. Cantor, G. Church & T. Sano, arXiv: 1206.6809 [astro-ph.IM]
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