Is dark matter a dinosaur killer?

DARK matter might live up to its ominous name. A recent theory about the behaviour of the elusive stuff leads to a scenario in which dark matter could be to blame for killing off dinosaurs. Last year, Lisa Randall at Harvard University and her colleagues suggested that dark matter can clump up into a thin, flat disc in a galaxy’s plane. As the solar system orbits the centre of our galaxy,  it bobs up and down on a regular cycle, so if the galaxy contains a dark matter disc, we would pass through it every 35 million years. In a study released last week, the team say that comet impacts on Earth appear to spike every 35 million years, perhaps because of dark matter perturbing comets within the solar system (arxiv. org/abs/1403.0576). While the timing is not a perfect match, the cycle could encompass the giant impact linked to dinosaur extinctions.