Supermoon Spectacle, Interstellar Comet Insights, and Mars' Ozone Mystery Uncovered

0:00 Avery: Welcome, listeners, to Astronomy Daily, the

0:02 podcast that brings the cosmos down to Earth.

0:05 I'm Avery.

0:06 Anna: And I'm Anna. We have a fantastic

0:09 show for you today, packed with news from our

0:12 celestial neighborhood and the farthest

0:14 reaches of the universe.

0:15 Avery: That's right, we'll be looking up at the

0:17 biggest supermoon of 2025,

0:20 tracking an interstellar visitor as it zips

0:22 past the sun and uncovering a strange

0:25 atmospheric mystery on Mars.

0:27 Anna: And to cap it all off, we'll be exploring a

0:30 mind bending new the that asks, what if

0:33 dark matter doesn't exist at all?

0:35 Avery: It's going to be a, um, big one.

0:37 Let's get started with a sight we can all

0:40 look forward to in our own night sky.

0:42 Anna: Indeed, after a year of seeing the Moon

0:45 looking a bit smaller than usual, we're in

0:47 for a treat next week.

0:49 11:48pm Eastern Time on

0:52 October 6, to be precise, which,

0:55 if I've done my math correctly,

0:57 corresponds to 3:48

1:00 UTC on October 7th

1:03 will see the biggest and brightest supermoon

1:05 of 2025.

1:07 Avery: I'm already marking my calendar. So for

1:10 our listeners who might be new to this, what

1:13 exactly makes a full moon a, uh,

1:15 supermoon?

1:16 Anna: It's all about the moon's orbit. It's not a

1:19 perfect circle, it's an ellipse. So

1:21 sometimes the Moon is at its farthest point

1:24 from Earth, which we call apogee. And

1:26 sometimes it's at its closest point, or

1:28 perigee. A supermoon happens when a full

1:31 moon coincides with its perigee.

1:33 Avery: And that makes it look bigger and brighter in

1:35 the sky. Right. I read it can appear up to

1:38 14% larger and 30% brighter than a

1:41 micro moon, which is when the full moon

1:43 happens at apogee.

1:44 Anna: Exactly. And we've just come through a period

1:47 of micro moons, so the difference will be

1:49 quite noticeable. This particular supermoon

1:52 is also the Harvest Moon, which is the full

1:54 moon closest to the autumnal equinox.

1:57 Avery: The harvest Moon. That's the one that

1:59 historically helped farmers bring in their

2:01 crops. Because it rises so close to sunset,

2:04 giving them extra light to work by, it often

2:07 looks huge and orange on the horizon.

2:09 Anna: That's the one. The orange color is due to

2:12 the same effect that makes sunsets red. The

2:14 light is passing through more of Earth's

2:16 atmosphere. So next week we get a combination

2:19 of things. The closest full moon of the year

2:22 and the beautiful effect of the harvest moon,

2:25 all making for a spectacular celestial event.

2:28 Avery: From something we can see with our own eyes

2:30 to something that requires a fleet of

2:32 interplanetary spacecraft.

2:34 Let's get an update on the interstellar comet

2:37 3i Atlas.

2:38 Anna: This is incredibly exciting.

2:41 3i Atlas is only the third

2:43 interstellar object we've ever detected

2:46 passing through our solar system. The first

2:48 was Oumuamua and The second was

2:51 2i Borisov. These objects are

2:54 cosmic messengers from other star systems.

2:57 Avery: And the European Space Agency is pulling out

2:59 all the stops to study this one. From now

3:02 until early November, they're planning to use

3:04 a trio of their spacecraft, the Mars

3:07 Express and ExoMars Trace Gas Orbiter,

3:10 which are both orbiting Mars, and the JUICE

3:13 spacecraft, which is on its way to Jupiter.

3:16 Anna: The reason this is such a unique opportunity

3:18 is because of the comet's trajectory. As it

3:21 makes its closest approach to the sun, it's

3:24 going to heat up dramatically. This heating

3:26 causes ices on its surface to sublimate,

3:29 turn directly into gas, releasing dust

3:32 and revealing the chemical composition of the

3:34 comet's nucleus.

3:36 Avery: So it's like unwrapping a gift from another

3:38 star. And using three different spacecraft

3:41 gives them a huge advantage, doesn't it?

3:43 Anna: It certainly does. Each spacecraft has

3:46 different instruments and will see the comet

3:48 from a different vantage point. This

3:50 triangulation allows scientists to build a

3:53 much more complete 3D picture of the comet's

3:56 activity and the mater its shedding. By

3:59 studying the composition of this gas and

4:01 dust, we can learn about the building blocks

4:03 of planets in whatever distant star system

4:06 this comet came from.

4:07 Avery: It's a reminder of how interconnected the

4:09 galaxy is. A piece of another solar system

4:13 just passing through for a quick visit.

4:15 Incredible.

4:17 Anna: Absolutely.

4:19 Now let's bring our focus a little closer to

4:21 home, to our planetary neighborhood,

4:24 Mars. Scientists have been puzzled

4:27 by a mysterious surge in ozone

4:30 that appears over its north pole during the

4:33 winter.

4:33 Avery: M ozone on Mars. I, uh, usually

4:36 associate ozone with Earth's protective

4:39 layer. Is it the same thing?

4:41 Anna: It's the same molecule. Three

4:43 oxygen atoms bonded together. But

4:46 on Mars, its behavior is very different.

4:50 Using the ExoMars Trace Gas Orbiter.

4:53 The same one. Watching the comet,

4:56 scientists noticed that ozone

4:58 concentrations in the middle atmosphere

5:01 spike during the winter inside the

5:03 polar vortex.

5:05 Avery: A, uh, polar vortex. We have those on

5:08 Earth too. Basically a giant spinning cyclone

5:11 of frigid air, right?

5:12 Anna: Precisely. And on Mars, it

5:15 gets incredibly cold inside this

5:17 vortex, dropping below minus

5:20 1, 130 degrees Celsius.

5:23 This cold is the key to the mystery.

5:26 Normally, water vapor in the atmosphere

5:29 reacts with other chemicals to destroy

5:31 ozone.

5:33 Avery: But when it gets that cold, the water vapor

5:35 freezes out, forming ice clouds.

5:38 So with the water vapor gone, the.

5:41 Anna: Ozone destroying chemical reactions Stop.

5:44 And the ozone is allowed to build up to

5:46 much higher concentrations than seen

5:49 anywhere else on the planet.

5:52 Avery: That's a clever piece of atmospheric

5:53 detective work. What does this tell us about

5:56 Mars?

5:57 Anna: It gives us a new way to trace the

5:59 circulation of gases in the Martian

6:02 atmosphere. And more importantly,

6:05 it helps us understand the history of water

6:07 on Mars. By tracking where and

6:10 when water vapor is present, we can build

6:13 better models of Mars past climate and

6:16 figure out where all its ancient water went.

6:20 Avery: From a mystery on Mars to the biggest

6:22 mystery in the entire cosmos. Ana, uh, we

6:25 have to talk about this new theory that

6:27 challenges the very existence of dark matter

6:30 and dark energy.

6:31 Anna: This is one of those ideas that could either

6:34 be a dead end or completely

6:36 revolutionized cosmology. The standard

6:39 model of the universe called Lambda

6:42 CDM tells us that about

6:44 95% of the universe is made of

6:47 two invisible components, dark

6:50 matter and dark energy.

6:52 Avery: Right. Dark matter provides the extra gravity

6:54 needed to hold galaxies together. And dark

6:57 energy is, ah, a force that's causing the

6:59 universe's expansion to accelerate. We can't

7:02 see them, but we infer their existence from

7:04 their effects.

7:05 Anna: Exactly. But physicist Rajendra

7:08 Gupta, uh, from the University of Ottawa, has

7:11 proposed a new model that gets rid of both.

7:14 His idea is based on a combination of

7:17 other theories, including one about tired

7:20 light and another covariing

7:23 coupling constants.

7:25 Avery: Whoa, those are some heavy terms. Let's break

7:27 that down. Covariing coupling

7:30 constants. What does that mean?

7:32 Anna: In simple terms? It means that the

7:34 fundamental constants of nature, things like

7:37 the strength of gravity or the

7:39 electromagnetic force, might not actually

7:42 be constant. They could be changing very,

7:45 very slowly as the universe ages and

7:48 expands.

7:49 Avery: So if the strength of these forces changed

7:52 over billions of years, how would that

7:54 replace dark matter?

7:56 Anna: Gupta's model suggests that these

7:58 changing constants could create effects that

8:01 we currently misinterpret as dark matter.

8:04 For example, the way galaxies rotate

8:07 much faster than they should, which is, uh, a

8:10 key piece of evidence for Dark matter could

8:12 be explained by these evolving physical

8:15 laws instead of an unseen particle.

8:18 The model also accounts for the accelerated

8:21 expansion of the universe without needing

8:24 dark energy.

8:25 Avery: So we might not be living in a universe

8:28 filled with mysterious dark stuff, but in a

8:31 universe where the fundamental rules are

8:33 slowly changing. That's a profound thought.

8:37 Anna: It is. It's important to stress that

8:39 this is still a very new and

8:42 untested hypothesis. The vast

8:45 majority of evidence still points towards the

8:47 standard lambda CDM model. But

8:50 it's a fascinating alternative that reminds

8:53 us to keep questioning our assumptions.

8:56 It shows that there are still huge

8:58 fundamental questions about our universe left

9:01 to answer.

9:02 Avery: And that is a perfect place to wrap up for

9:04 today.

9:05 From a supermoon in our backyard to an

9:07 interstellar comet, a Martian weather

9:09 mystery, and a whole new way to think about

9:11 the universe itself, it's been a.

9:14 Anna: Whirlwind tour of the cosmos. Thank you so

9:17 much for joining us on Astronomy Daily. If

9:19 you'd like to see more details on these

9:21 stories and more, please visit our

9:23 [email protected]

9:26 and check out our continually updated

9:28 newsfeed. And while there, you may like to

9:31 sign up for our free daily newsletter as

9:34 well.

9:34 Avery: Join us again tomorrow as we continue to

9:37 explore the wonders of the universe. Clear

9:39 skies, everyone. And remember to keep looking

9:41 up, especially this week.