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Hank: There’s usually a lot of concerning news going around about the Earth’s atmosphere, but a recent report in the journal Science has a positive claim: the ozone layer is healing! Ozone, or O3, is a molecule that’s being created and broken down all the time in the stratosphere, and it absorbs a lot of the Sun’s harmful UV-B radiation.

The “hole” is a severely reduced region of ozone above Antarctica that was discovered in the 1980s... along with a lot of depletion everywhere. See, these chlorine-containing chemicals in things like aerosols and fridges – called CFCs – turned out to destroy ozone way faster than it could naturally regenerate. The 1987 Montreal Protocol and other international agreements put the brakes on CFC use, but scientists still debate how much ozone levels are actually recovering – especially since late-2015 data showed the Antarctic hole had reached a nearly record-breaking size.

A team of researchers, led by Susan Solomon from MIT, have been using a bunch of atmospheric measuring and 3D modelling techniques to track ozone levels – past, present, and predicted future. Up until now, scientists typically studied October measurements, when the hole’s biggest during the year because of ideal conditions for ozone-depleting reactions. It’s cold enough to form clouds in the stratosphere, where more reactive chlorine gases are created, and bright enough, which provides energy.

But the Antarctic temperature and air movement in October change a lot from year to year, which skews the size of the hole and makes it harder to observe bigger trends. Meanwhile, September’s weather is a little more stable, which reduces these size variations. Based on a September dataset, the team suggests that Antarctica’s ozone hole seems to have been recovering – by an area around the size of India since 2000! But, by their estimates, it’ll still take at least 3 or 4 decades to get back to pre-CFC levels.

They suggested that the late 2015 measurements were a setback caused by a the eruption of the Calbuco [kahl-boo-co] volcano in Southern Chile earlier that year. Volcanoes can spew sulfur into the stratosphere, which can enhance the ozone-depleting chemical reactions. Now, the atmosphere is an incredibly complex system, and their model has some puzzles.

In fact, they suggest only about half of the ozone healing is due to the ban on CFCs, which was thought to be a primary factor. And the other half might be related to a shift in polar weather. So without fully understanding the reasons for the ozone recovery, we can’t say for sure whether it’s gonna get better or worse -- or even if their model’s accurate. So we can appreciate the good news, but we shouldn’t use it as an excuse to be lazy. If anything, it shows us that there’s still so much above our heads that we don’t understand.

Now, thinking about inside our heads: this week, two researchers from Stanford University published a communication in Cell Press calling for more research on the effects of MDMA, commonly known as ecstasy. MDMA is what’s known as an “empathogen” – it heightens feelings like closeness and empathy for the people around you. So, the researchers believe that studying how the drug affects the body and brain could lead to pharmaceuticals that help people with certain disorders or mental illnesses, especially related to social behaviors.

MDMA became popular in the early 1980s and was soon classified as a Schedule 1 drug – a category for substances with “no currently accepted medical use and a high potential for abuse.” So, research on MDMA plummeted, too. But in the last 30 years, we’ve developed all kinds of new genetic and imaging techniques. And the Stanford researchers believe these scientific tools could be useful in MDMA studies, but the drug’s taboo image is keeping scientists from doing this kind of research.

Now, to be clear, they aren’t advocating for the full legalization or recreational use of illegal drugs. Instead, they make the case that more scientists should study it with fair regulations, and without concern that studying a drug like MDMA might hurt their career. They also want to explore if MDMA’s Schedule 1 categorization is still useful.

Or, whether it has a place in medicine as a heavily-restricted Schedule 2 substance, like oxycodone or Adderall. Some small studies have been done, but they’re few and far between. For example, some very early case reports from 1990 suggest that MDMA could help people with PTSD, by helping them build a trusting relationship with their therapist.

There have also been a couple more recent studies on rats and mice, monitoring how their brains respond to MDMA and what other neurotransmitters might be involved. But when it comes to humans, the gaps in our knowledge are huge. So these scientists are echoing the feelings of the UK researchers that we talked about earlier this year, who published partially-crowdfunded research on LSD. Basically, they suggest that our understanding of how these illegal drugs work will remain as underground as the substances themselves – unless more researchers conduct carefully-controlled experiments.

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