Traces of ancient viruses are littered throughout the human genome, embedded within the DNA's structure. Scientists already knew that some of these viral artifacts can "activate" in cancer cells and potentially contribute to the disease's progression — but now, a new study reveals that the viruses are active in dozens of healthy tissues, too.

RALEIGH, N.C. (Ivanhoe Newswire) – Surgeons at Duke University Hospital performed the world’s first combination heart transplant and thymus tissue implantation and now, a year later, their 18-month-old patient is a growing, thriving medical miracle.

After dominating the Earth for more than 160 million years, the dinosaurs finally met their doom thanks to a visitor from space. Around 66 million years ago, an asteroid measuring at least 6 miles (10 kilometers) across dealt the dinosaurs' world a devastating blow, triggering earthquakes, tsunamis, volcanic eruptions and climate catastrophes that soon rendered 75% of all living creatures extinct.

But, through all this, Earth itself remained.

Does this mean our planet is immune to an asteroid Armageddon? If the dreaded dino-killing asteroid wasn't enough to end the world, then what would it take? Could a space rock actually destroy the entire Earth — and how big would it have to be?