Wuhan's Huanan Seafood Market is associated with many of the first cases or Covid- 19, but data on precisely how and from where the virus might have first spread has been difficult to find. However a re-examination of the earliest samples collected from the market seem to pinpoint where the virus first showed itself. Sydney University virologist Eddie Holmes says this evidence will be crucial in determining which animals may have initially passed the virus to humans.

Humans are known to have passed the Sars-Cov-2 virus to other animals, including cats, mink and deer. Canadian researchers have recorded the first incident of a modified form of the virus passing back from deer to humans. Virologist Samira Mubareka from the University of Toronto explains the implications.

Chernobyl, the site of the worlds worst nuclear accident is back in the news as the Russian invasion of Ukraine led to a stirring up of nuclear material when troops entered the site. Ukraine has a number of nuclear reactors, Claire Corkhill, professor of nuclear materials at Sheffield University explains the potential risks from the current conflict and safeguards in place.

And we hear from Svitlana Krakovska Ukraine's representative on the Intergovernmental panel on Climate Change, on her thoughts on the prospects for climate action and scientific progress in The Ukraine.

Also, If you took a fly into a really tall elevator and let it out at the top, would it still be able to fly? And what’s the absolute highest an insect could possibly go? It’s a question that’s been bugging CrowdScience listener Chee for a while, but presenter Alex Lathbridge is on the case.

He discovers that when they’re not buzzing around your lunch, insects can be routinely found flying high up in the atmosphere travelling from A to B. There are also ground-dwelling bumblebees living in the mountains of Sichuan, China that have demonstrated an ability to fly at altitudes higher than the highest point on the planet.

But leaving aside how high insects DO fly, how high COULD they fly if given the chance? Alex explores the theoretical limits of insect flight with the help of a bit of biomechanics – before contemplating the ultimate heights of the International Space Station where the mystery of whether a fruit fly will fly in zero gravity is finally answered.

Image: Disinfection Work At Wuhan Huanan Wholesale Seafood Market, China 4 March 2020. Credit: Zhang Chang / China News Service via Getty Images.