IRA FLATOW: This is Science Friday. I’m Ira Flatow.

We had some sad news from the conservation world this week. Sudan, the last male northern white rhino, died at the age of 45. His death leaves his subspecies teetering on extinction because there are only two females remaining, his daughter and granddaughter. But hope remains because– well, here to explain why is Rachel Feltman, Science Editor at Popular Science. Welcome back Rachel.

RACHEL FELTMAN: Thanks for having me Ira.

IRA FLATOW: Give me some hope, Rachel.

RACHEL FELTMAN: Yeah, so the good news here is that researchers have already been working for several years really to prepare for Sudan’s death. The thing is that neither of the two females are capable of carrying calves for various medical reasons, but they do have potentially viable eggs. Sudan was still producing viable sperm up until he died. And they were collecting that pretty regularly. There’s also sperm from several other deceased northern white rhino males.

So the plan is to harvest eggs from Sudan’s daughter and granddaughter, fertilize them, and then implant the embryos in southern white rhinos, which is the other white rhino subspecies. And there are actually about 20,000 of them. So they’re quite abundant. They’re the only– they’re arguably the most successful rhino, especially in Africa.

IRA FLATOW: But they really want bring back the north. He’s a different rhino, right?

RACHEL FELTMAN: Yeah. So subspecies sometimes can feel a little bit like splitting hairs. And if there are 20,000 white rhinos in total, why do we care that the northern is going extinct? But the southern and northern rhinos have been separated for a really long time. One study estimated up to a million years. So they really are unique animals. They live in very different parts of Africa. And so most conservationists agree that if we can save the northern white– which by the way, is only teetering at the edge of extinction because of things we did, like poaching and habitat destruction. Most people agree that if we can do anything to save the northern white, we should.

IRA FLATOW: OK. Let’s move on to something about the carbon footprint of our food.

RACHEL FELTMAN: Yeah. So most of us know that eating meat is not great for the environment. It produces a lot of greenhouse gas emissions.

IRA FLATOW: Also takes a lot of water–

RACHEL FELTMAN: It does.

IRA FLATOW: –to feed a cow.

RACHEL FELTMAN: It does. Cows burp and fart a lot of methane. So just on the whole, not a great source of food from an environmental perspective.

So a lot of people, a lot of average Americans try to cut down on their animal-product consumption, which is great. But it hasn’t really been clear what the distribution is in terms of how people are contributing to our carbon footprint from diet. And this new study, which compared survey diet data with information about food emissions, found that 46% of our food emissions come from just around 20% of us. So they found that there’s this group of a fifth of Americans that just eat so much more beef than average that they’re producing eight times the emissions as the lowest percentage of people. And 72% of those emissions came directly from beef.

IRA FLATOW: Wow.

RACHEL FELTMAN: Yeah, the difference between lowest and highest is almost entirely due to beef.

So on the one hand, it’s like a little disparaging for, speaking personally, as somebody who eats like a slightly below average amount of animal products and is always trying to eat less, because what we really need to do is get these super heavy meat eaters to eat an average diet. The country doesn’t have to go vegan. We just need to get the people who are eating the most meat to eat like an average amount.

IRA FLATOW: Good luck on that.

RACHEL FELTMAN: Yeah, we’ll see.

IRA FLATOW: So we’ll move on to New Zealand, I understand, has some good news. They’ve cleared a tiny, unpopulated island of invasive mice.

RACHEL FELTMAN: Yes, it took $3.6 million and several years to kill 200,000 mice, which is very important because there are no native mammals in New Zealand. And this island in particular, the Antipodes has a bunch of plants and animals that don’t exist anywhere else in the world because of its total isolation.

That isolation, by the way, meant that researchers had to actually climb up sea cliffs to get to the island. There’s no harbor for a boat to bring them into. Then they lived there for several months. They deposited over 140,000 pounds of mouse poison. And then they had to wait a couple of years because even if a couple of mice had escaped the poison, they would have been able to totally repopulate the island. And they actually eat the chicks of these birds that don’t exist anywhere else and have no natural predators there, so they can just wreak total havoc. But it seems that they were successful, so now there are no mice left.

IRA FLATOW: Well, if my math is right, that comes to about $6.00 a mouse.

[LAUGHTER]

So I like that. It’s pretty worth their money.

Finally, we’re not doing a good thing, bad thing this week, but you have a story that fits that mold perfectly about the TRAPPIST-1 exoplanet system, right?

RACHEL FELTMAN: Yeah. Well, we’re so used to hearing scientists talk about water on other planets as being such a cool thing. It’s the baseline ingredient for life. So when we say a planet is potentially habitable, it better have water.

A really cool study this week showed that the planets in the TRAPPIST system, which was in the news a lot last year, might have too much water for life, like way too much.

IRA FLATOW: You can have too much water?

RACHEL FELTMAN: You can have too much. We’re talking about– so earth has something like 0.02% of its mass made up by water. And we’re a pretty wet planet as they go. These planets have maybe 5% to 10% or even 50% of their mass taken up by water. And we don’t even know what that looks like. We’re talking about planets where everything down to the very closest bit you can get to the core is water. So physically we don’t really understand totally how that would work. And also just the geology would be so different that, at least based on our understanding of how life works, there would be not enough of the molecules that are the building blocks of cells.

So of course, this comes back to the question of like, how do we know that life on other planets is anything like ours? So maybe there is some kind of crazy life swimming around on these super weird wet TRAPPIST planets, but we certainly wouldn’t be able to detect it based on what we know about life.

IRA FLATOW: Well, that’s two hopeful stories you’ve brought to us this week. Yeah, you know, because you’re right, how do we know? We just assume that life is like ours and that’s how we have to look for it, because those are the tools we have. You’ve got to work with the tools you have. Thank you Rachel.

RACHEL FELTMAN: Thank you.

IRA FLATOW: Rachel Feltman, science editor at Popular Science.

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