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About 66 million years ago an asteroid at least 6 miles wide crashed into the Earth, in the shallow sea that is now the Yucatan Peninsular in Mexico. It gouged the Chicxulub crater 18 miles deep; threw 25 trillion tonnes of debris into the atmosphere, much of which was hotter than the Sun, created huge seismic waves and massive tsunamis churning the Gulf of Mexico, tearing up coastlines and peeling up 100鈥檚 of metres of rock. 75% of the Earth鈥檚 forest burned. Debris was thrown out across the Solar System and North America was showered by a fan of glassy molten rock droplets. This geological event marked the end of the Cretaceous period and the start of the Palaeogene. Most people accept that this massive event caused the last great extinction, the end of the dinosaurs and a period of intense cold. Many fossil finds back this theory up. But very little fossil evidence showing the impact of the actual event has been found. Until now. Hundreds of miles from Chicxulub in a fossil site called Tanis, in North Dakota, part of the vast Hell Creek formation, is a fossil find that depicts the turmoil 10's of minutes after the asteroid hit. Marine and freshwater fish are found tangled together with these glassy droplets crammed in their gills, Charred trees are mixed up with hundreds of mangled animal bones, amber perfectly preserving drops of what was molten Earth. It's got palaeontologists including Professor Phil Manning at Manchester University very excited.

The gravitational wave detectors LIGO and VIRGO have been recently upgraded and made more sensitive to the miniscule signals that denote ripples in gravity - gravitational waves. Professor Sheila Rowan of the University of Glasgow explains to Gareth Mitchell that she hopes that with this third run of the detectors, they will be finding not just one or two signals that provide evidence of massive events in our universe, but hundreds, maybe even thousands.

In the quest to understand how corals are affected by rising sea temperatures we need to understand the symbiotic relationship they have with dinoflagellates, the single-celled algae that live in, and use photosynthesis to make food for the coral. When coral gets too hot and undergoes 'bleaching', this is the algae leaving the coral. Yixian Zheng at the Carnegie Institution of Washington takes Roland Pease on a tour of her coral tanks and explains that she's hunting for a model coral organism to study this process at the genetic and molecular level.

A crime has been committed in the studio. Gareth's tea has been drunk and his biscuits have been nibbled. Luckily evidence was left at the scene of the crime - a shoeprint with distinctive wear patterns. One quick phone call and the director of the Leverhulme Research Centre for Forensic Science at the University of Dundee, Professor Niamh Nic Daeid is on the case. She's asking the public to help build up a database of footwear prints. The project is the largest ever study into the variation in footwear marks made by the same shoes across different surfaces and activities so that the variation observed can be used to explore links between the shoe and the mark it makes. In order to do this, she's asking thousands of individuals to take part in a large-scale citizen science project by taking pictures of their footwear and the marks they make. This will help the Dundee team build a substantial database for use in their research to aid the scientific validation of footwear marks as evidence for use in the criminal justice system.

Producer (and biscuit thief) - Fiona Roberts