Lab notes: we are starlight, we are slug slime ...

Look up to the skies and see ... This week’s science has shone a light on our galaxy’s origins and unexpected water on the moon. Photograph: Shivang Mehta/Barcroft Images

This week’s biggest stories

Proving that Joni Mitchell is one of the greatest astrophysicists of our time (followed closely by Moby, obviously,) simulations have revealed that up to half the material in our home galaxy – and by extension in our bodies – arrived from smaller galactic neighbours, as a result of powerful supernova explosions. Add to this the news that the moon is wetter than we thought, which raises new possibilities for lunar exploration, and frankly, I’m starting to feel positively intergalactic. Back here on Earth, however, the picture is a mixture of optimism and concern. On the one hand, an extremely exciting piece of research (described as a “tour de force” by one expert, so there you go) has shown that the hypothalamus controls ageing, and that implanting stem cell from it into the brains of mice slowed their rate of ageing and kept them mentally and physically fit for longer. They’re hoping to conduct human trials soon. So far so life-affirming, but on the other hand we have the rather worrying news that sperm counts among western men have halved in last 40 years. Nobody seems to know why, and it appears that this is partly because men’s reproductive health is a rather neglected area. Researchers have also found a strong association between consuming higher levels of sugar and depression in men (a link not seen in women). Looks like we need to start paying better attention to men’s health – mental and physical – or all that extra old age spent bouncing around our moon colony is going to be no fun at all.

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Under-celebrated creature of the week

I admire you, slug. But keep your distance from my lovely leaves, if you please. Photograph: chris brignell / Alamy/Alamy

All hail the humble slug, unwelcome in my garden, but inspiration for what may become a surgical staple - or rather, glue.

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Straight from the lab – top picks from our experts on the blog network

Once we’ve settled this whole cat/dog thing we’ll get onto the real question: panda or red panda? I know where I stand - do you? Photograph: Robert Bahou/Rex Shutterstock

Cats vs dogs: in terms of evolution, are we barking up the wrong tree? | Lost Worlds Revisited

Are you a dog person, or a cat person? The question is often treated as dichotomous: if you appreciate the solidity of a steadfast pooch, you can’t also relish the coquettish companionship of a kitty. Recent studies suggest humankind could have been divided by their pet-preferences since the stone age. In evolutionary terms, however, the question is far from black and white. Cats and dogs belong together, related to one another by a common ancestor. They share this ancestry with a whole suite of other animals, large and small. One may as well ask: are you a badger person, or a hyaena-person? Do you prefer meerkats, or weasels?

What does the US election integrity commission need to be credible? Some actual experts | Political science

Our assessment of the first meeting is that, as currently structured, the commission will almost certainly create more problems than it solves. The most remarkable thing about the first meeting is not who was there and what was said, but rather who was not there and what was not said.

Is it always good to talk? How to help survivors of trauma | Sifting the evidence

In the wake of Grenfell Tower, 300 counsellors have volunteered to be available for survivors and firefighters to give free therapy should it be wished for. This offer of help is deeply compassionate. It also needs careful thinking through. There is good evidence for talking therapies. But if a talking therapy has the power to help, it can also have the power to harm, and the human instinct to offer support needs to be weighed carefully against the mixed evidence available on early post-trauma intervention.

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Science Weekly podcast

Minds and machines: can we work together in the digital age? Photograph: Issei Kato/Reuters

This week Ian Sample is joined by Andrew McAfee and Erik Brynjolfsson, who lay out their blueprint for the future of the workplace, including the role big data will play, how some processes involving decision-making could be automated, and how minds and machines can come together to cancel out each other’s errors.

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Eye on science – this week’s top images

Auroral Crown by Yulia Zhulikova. Gorgeous. Just gorgeous. Photograph: Yulia Zhulikova/National Maritime Museum

What a treat: it’s once again time for the Astronomy Photographer of the Year 2017 shortlist, and this year’s breathtaking entries don’t disappoint.