[Rockhounds] Astronomers: A comet fragment, not an asteroid, killed off the dinosaurs

[Kreigh Tomaszewski]

Jupiter's gravity pushed comet toward Sun; comet was ripped apart by tidal
forces.
Some 66 million years ago, a catastrophic event occurred that wiped out
three-quarters of all plant and animal species on Earth, most notably
taking down the dinosaurs. An errant asteroid from the asteroid belt
<https://en.wikipedia.org/wiki/Asteroid_belt> has been deemed the most
likely culprit. However, in a new paper
<https://www.nature.com/articles/s41598-021-82320-2> published in
Scientific Reports, Harvard astronomers offer an alternative: a special
kind of comet—originating from a field of debris at the edge of our solar
system known as the Oort cloud
<http://their%20findings%20also%20offer%20evidence%20that%20the%20unusual%20composition%20of%20the%20chicxulub%20impactor%E2%80%94carbonaceous%20chondrite%E2%80%94indicates%20it%20originated%20from%20the%20oort%20cloud%2C%20and%20not%20from%20the%20main%20asteroid%20belt%2C%20as%20suggested%20by%20one%20of%20the%20more%20popular%20origin%20theories.%20it%27s%20a%20rare%20composition%20for%20main-belt%20asteroids%2C%20but%20common%20among%20long-period%20comets.%20the%20authors%20also%20point%20to%20other%20impact%20craters%20with%20similar%20composition%2C%20most%20notably%20the%20vredefort%20crater%20in%20south%20africa%E2%80%94the%20result%20of%20an%20impact%20some%202%20billion%20years%20ago%E2%80%94and%20the%20zhamanshin%20crater%20in%20kazakstan%2C%20from%20an%20impact%20within%20the%20last%20million%20years.%20those%20times%20frames%20are%20in%20line%20with%20siraj%20and%20loeb%27s%20calculations%2C%20which%20indicate%20such%20objects%20should%20strike%20earth%20once%20every%20250%2C000%20to%20730%2C000%20years./>—that
was thrown off course by Jupiter's gravity toward the Sun. The Sun's
powerful tidal forces then ripped pieces off the comet, and one of the
larger fragments of this "cometary shrapnel" eventually collided with Earth.
https://arstechnica.com/science/2021/02/astronomers-a-comet-fragment-not-an-asteroid-killed-off-the-dinosaurs/