Author: BBC World Service

Listener Julie lives close to the coast in New Zealand and wants to know why the water that washes up on the beach isn't fresh. How exactly does all that salt get into the world's oceans?

In India, a country where salt became symbolic of much more than well-seasoned food, host Chhavi Sachdev visits coastal salt farms and a research institute dedicated to studying all things saline, to better understand our relationship with salty seas.

The team also ventures to a very briny lake on the other side of the globe in Salt Lake City, Utah, to learn how salt makes its way into water bodies.

Speaking to an expert in deep sea exploration, we learn how hydrothermal vents may play a role in regulating ocean saltiness, and how much the field still has to explore.

Meanwhile, listener Will wants to know how much melting ice sheets are affecting ocean salinity. But ice melt isn’t the only thing affecting salt levels when it comes to the impacts of climate change.

And... how many teaspoons of salt are in a kilogram of sea water anyway? We do the rigorous science to answer all these salient saline questions.

Featuring: Deepika - small scale salt farmer Mark Radwin - PhD candidate in geology and geophysics at the University of Utah Brenda Bowen - Geology & Geophysics, Atmospheric Sciences, University of Utah Chris German - Geology & Geophysics, Woods Hole Oceanographic Institution Prasan Khemka - Chandan Salt Works Paul Durack - Lawrence Livermore National Laboratory Bhoomi Andharia - Central Salt & Marine Chemicals Research Institute

Presenter: Chhavi Sachdev Producer: Sam Baker Editor: Cathy Edwards Production Coordinator: Liz Tuohy Studio Manager: Sarah Hockley

(Photo: Shiv Salt Works, Bhavnagar, Gujarat in India. Credit: Chhavi Sachdev, BBC)

Could a scientific burger compete against the fast food giants? We fear not!

You will need: • Meat - A tick capable of inducing alpha gal syndrome, a disease that makes you allergic to red meat. • Garnish - Lettuce grown in space. (WARNING: it is more susceptible to bacterial infection than that grown on Earth). • Buns - A short but thick guide to the human buttocks with Heather Radke. Why do we humans have such large behinds? • Something sweet - We chose the humble baobab seed. An unusual tree indigenous to Madagascar, the subject of an incredibly successful conservation project. • Fries - Of course! The humble potato is threatened by climate change, what is being done to futureproof it?

Instructions: • Who are we kidding! There is no scientific method! • Bang it all together and feast your ears on this week’s show!

Presenter: Marnie Chesterton Panellists: Candice Bailey and Affelia Wibisono Producers: Harrison Lewis, Julia Ravey, Ben Motley and Noa Dowling

With mice being the latest species to carry the disease, pandemic expert Rick Bright calls for stronger counter measures. “It’s like PTSD from February 2020” he says. The authorities in the USA are responding too slow to the spread of H5N1 bird flu through its dairy farms – even mice are carrying the virus now, and not enough is known of how it is evolving and whether humans are threatened. He talks Roland through the complex political and public health issues.

Child sacrifices in the Mayan empire a thousand years ago have been confirmed with DNA evidence from bones recovered in the 1960s from an underground pit. Some victims were twins, possibly indicating a brutal ritualistic re-enactment of an ancient myth involving divine twins. Geneticist Rodrigo Barquera describes the analysis.

Mature orchids perform a unique form of offspring-care, feeding tiny seedlings with nutrients via networks of thread-like fungal hyphae in the soil, according to experiments conducted at Sheffield University. Mycologist Katie Field has been delving into this underground sustenance network.

Geoscientists at the edge of the Arctic ocean are looking for ancient clues to the stability of the Atlantic circulation that brings critical warmth to Europe and the northern hemisphere. Could past changes help unravel the influence of global warming? Roland talks to Renata Lucchi in the control room of Research Vessel JOIDES Resolution.

Presenter: Roland Pease Producer: Alex Mansfield Production Co-ordinator: Jana Bennett-Holesworth

(Image: Mouse sitting on grain. Credit: SAEED KHAN/Getty Images)

CrowdScience listener Eleanor was lying in bed one rainy evening, listening to the radio. She lives in New Zealand, but happened to hear a weather forecast that told her it was raining in the UK too.

She started wondering: could it be the same rain falling there and outside her window in New Zealand? Can a raindrop really travel all the way around the world?

There are a number of routes the droplet could take, including traveling as moisture in the air. Presenter Caroline Steel meets meteorologist Kei Yoshimura, who puts his powerful weather simulation to work plotting the raindrop’s journey through the sky.

What if the raindrop falls along the way and gets trapped? Where might it end up? Hydrologist Marc Bierkens talks Caroline through the detours it could take, ranging from short stop-offs in plant stems to extremely long delays in deep groundwater.

Finally, could the drop of water make it to New Zealand by circulating through the world’s ocean currents? Oceanographer Kathy Gunn maps the droplet’s path through the ocean – and explains how climate change might affect its journey.

Featuring: Prof. Kei Yoshimura, Professor of Isotope Meteorology, University of Tokyo Prof. Marc Bierkens, Professor of Earth Surface Hydrology at Utrecht University Dr. Kathy Gunn, Lecturer in Climate Sciences at the University of Southampton

Presenter: Caroline Steel Producer: Phil Sansom Editor: Cathy Edwards Production Co-ordinator: Liz Tuohy Studio Manager: Tim Heffer Additional recording: Knut Heinatz

(Photo: Textures of rain on the surface of the ocean. Credit: Philip Thurston/Getty Images)