It’s the central question for the current generation of Mars missions. Since the first close-up pictures of the red planet back in 1965, decades of space missions have revealed our neighbouring planet to be cold, rocky and sterile. But there are hints of a more dramatic past; of raging volcanoes and flash floods. Could this be a planet where life existed? Could life still exist under the surface? And could humans live there, or even travel the distance to get there safely, at some point in the coming decades?

CrowdScience listeners from Australia, Ghana and Canada have been musing on all sorts of Martian matters. Presenter Marnie Chesterton visits a corner of Stevenage, UK, with a distinctly unearthly appearance and takes a virtual tour of the Martian atmosphere. She also puts listeners’ questions to the scientists designing the spacecraft and instruments they hope will unlock the secrets of Mars.

(Image: illustration of Mars shot from space. Credit: Getty Images)

The idea of creating underwater habitats has captured the imagination of writers, thinkers and scientists for decades. However, despite numerous grand visions, these dreams of aquatic metropolises have not yet come to fruition. Crowdscience listener and scuba enthusiast Jack wonders whether - given improved technology and the growing environmental pressures facing humans on land - it is time to reconsider the ocean as an alternative permanent living space for humans.

Marnie Chesterton dons her flippers for Crowdscience in search of the oceanographers and architects who have dedicated their lives to designing vessels, labs and underwater habitats. She explores whether oceanic cities remain a sci-fi dream or a realistic solution to some of our modern challenges. Can the oceans’ largely unexplored resources be harnessed to support living underwater?

(Photo: Illustration of a modern city under the sea. Credit: Getty Images)

What is light and can we trap it in a box? On this edition of CrowdScience, Marnie Chesterton brings you a kaleidoscope of colourful questions from listeners around the world, from Kampala to Chicago. Shireen asks why people have a favourite colour and whether other animals show colour preferences too. Marnie heads to the zoo to see what the birds, bees and butterflies think. There, she meets a colour-changing chameleon to find out how and why it does because of a question from Dramadri in Uganda.

Meanwhile, Paul in Melbourne is interested to know more about colour blindness. And finally, Feroze asks why we only see a portion of the electromagnetic spectrum and wants to know if we might, one day, hack our vision to see beyond the seven colours of the rainbow.

Presenter: Marnie Chesterton

(Photo: Stardust and magic in a woman hands on a dark background. Credit: Getty Images)

Hedgehogs are the UK’s favourite British mammal. They have cute furry faces, a snuffly nose and the ability to gobble up garden slugs. What’s not to like? Answer: quite a lot if you live in the Outer Hebrides. Hedgehogs were introduced to South Uist in the 1970s as garden pest controllers, but are now serious pests in their own right – munching their way through the eggs and chicks of globally important wading bird populations. This emblem of cuteness is really a killer. So what’s to be done?

That’s the quandary facing this week’s CrowdScience thanks to a question from Juan Carlos in Cuba. He wants to know how different parts of the world are dealing with invasive species – one of the biggest threats to global biodiversity. Presenter Anand Jagatia heads to the Uists to hear how having an invader that’s loved by millions can cause a whole host of problems. He also discovers how various warring parties eventually came together to solve this very prickly problem.

Also in the programme, Anand travels to South Africa to find out how researchers are coping with invasive trees by introducing another non-native species. While in the Caribbean, we hear how people are dealing with invasive fish by eating them.

Presenter: Anand Jagatia

(Photo: A European hedgehog. Credit: Getty Images)

Teenagers are known for ignoring their parents’ advice, but is this reputation for rebellion well-founded? If so, is rejecting the advice of previous generations and treading our own path an important part of what it means to be human? Are we successful as a species precisely because of our questioning natures?

Marnie Chesterton and a panel of experts look at the science of taking advice and making decisions, finding out how human curiosity and exploration compare to other animals, learning the best ways to give and take advice, and seeing whether we’re more likely to trust artificial intelligence than the wisdom of our elders. Finally, we give listener Hans some expert advice on whether or not to keep nagging his kids.

Presenter: Marnie Chesterton

(Image: A father and son having communication issues. Credit: Getty Images)

This deceptively simple question from listeners Andy, Mike and James is actually one of the hardest questions CrowdScience has ever tackled. Why? Because even scientists struggle to explain the true nature of the magnetic force and to do so in a way that even presenter Marnie Chesterton can understand is a serious challenge. What is a magnet? And just what is going on when magnets exert a force?

With the help of Melanie Windridge, Sean Giblin, Steve Bramwell, Charlotte New and Peter Morris we attempt to navigate the oddities of one of the most fundamental phenomena in the universe.

(Image: A horseshoe magnet attracting some hammer nails. Credit: Getty Images)

Anand Jagatia heads to the rainbow nation of South Africa, to answer listener Lucy’s deceptively simple question. He follows the path of early human migration to understand the relationship between light skin and latitude, and find out how the world become more multi-coloured as people ventured further away from the equator. And he learns how our genes have helped us adapt to less sunny environments, hearing from the remote KhoeSan tribe in the Kalahari desert, who took part in a massive study aimed at giving scientists a better understanding of pigmentation.

Producer: Marijke Peters

(Image: Four diverse women’s arms holding each others wrists in a circle. Credit: Getty Images)

Listener Pogo wants to know why there aren’t any cabbages – or any of the other vegetables – in his local forest. Where did they all come from? And could they someday disappear? Presenter Gareth Barlow goes hunting for wild snacks in a city park and unearths the evolution of our most beloved greens. The vegetables on our supermarket shelves today were not always nicely wrapped and tasty. Humans have been selecting for specific genes in plants for thousands of years by choosing to grow those we liked the most.

Tomatoes have been transformed from a small prickly desert plant in Peru into a water guzzler with round, juicy, sweet fruits. But with breeding – and sometimes cloning – of plants we have also created genetic bottlenecks in many of the crops we rely heavily on. This has left many of our vegetables across the world vulnerable to shifts in climate, natural disasters, wars and diseases.

To find solutions to this massive breach in food security, CrowdScience heads to the Millennium Seed-bank in England. By collecting and storing our most precious seeds in vaults beneath the ground, scientists are protecting the genetic diversity that we will need to overcome the challenges ahead.

Presenter: Gareth Barlow

Picture: Man holding basket of vegetables

Sex – for most organisms - is about meeting the right partner. But what if you and your mate are stuck far apart with no ability to travel? This dilemma could put a bit of a downer on your sex life, but is faced by plants everywhere. Presenter Anand Jagatia uncovers the happy fact that not only have plants overcome this problem, they positively excel at it. From hay fever to honey, the sexual strategies of plants affect us daily, and we couldn’t live without their success. In this episode, CrowdScience is answering the questions you sent after a previous episode entitled ‘Can plants talk?’ which explored the way plants and trees use a fungal network to communicate. This time, we explore how plants ‘feel’ bees as they fly past, and more complex communication involving the ‘wood wide web’.

Presenter Anand Jagatia

(Image: A yellow dandelion flower attracts a pollinator in the evening sunlight. Credit: Getty Images)

Some of the biggest reserves of freshwater are right under our feet and they're really important for farming as well as providing us with water to drink. However, in some areas of the world, groundwater is being slurped up quicker than it can be replenished. In fact, about 1.7 billion people live in regions where groundwater is under stress, 60% of them in India and China. This figure is set to rise as the climate changes and as the population grows.

CrowdScience listener Waheed from Afghanistan wants to know if we will run out of groundwater and what the repercussions might be. Marnie Chesterton trots around the globe to find out, starting with a row on the River Thames before hearing from Afghanistan to understand what’s happening where Waheed lives. She learns of what has happened to London, Mexico and Malta when they over pumped their aquifers. Finally, Marnie looks to Bangalore where the population is booming to understand how they’re coping with increasing demands on water.

Presenter: Marnie Chesterton

(Image: Children holding their hands up - asking for drinking water. Credit: Getty Images)