After a holiday break from writing, I’m back and attending the American Astronomical Society meeting this week. Normally, I’d be traveling to a distant city for this meeting. However, during the Age of Pandemic, all events like this have gone virtual. So, thousands of us have been logging into the meeting to sip from the “Firehose of Astronomy Results.”

This year’s meeting offered talks and papers about everything from planetary science to cosmology, so let’s dive in! Over the next week or so, I’ll bring you some highlights of the kinds of science that has astronomers excited.

Pluto Raises Questions

We’ll start with Pluto.  You remember Pluto. It’s the little planet that just keeps on giving.  Before the New Horizons mission flew through the Pluto system in 2015, planetary scientists had a few problems with it.

First, it’s pretty far away. Looking at it through a telescope didn’t reveal a lot. Not even Hubble Space Telescope could show much in the way of surface information about Pluto.  That is, in fact, why New Horizons exists. It is on a forever journey to the Kuiper Belt and beyond.

The second problem was Pluto’s size. It appears small from Earth. Also, it didn’t fit the definition of a “planet.” So, some researchers thought it should NOT be a planet.  Now it’s called a “dwarf planet.” That happened long before New Horizons even GOT to Pluto. So, there were two strikes against it. The third strike was that, due to that distance, and the temperatures and other characteristics of this part of the solar system, imaging and studying this world would be challenging. So, the New Horizons team planned for that with a suite of instruments specially tailored for the conditions.

New Horizons Provides Some Answers

Well, it all paid off. New Horizons returned its own version of the firehose of astronomy all from three worlds we never expected to be so fascinating. We all remember the amazing images of Pluto and Charon, and then a few years later, of the Kuiper Belt Object Arrokoth.  They showed us that Pluto is not only NOT a dead world, but it’s alive geologically. It has surface areas that appear to be pretty young and could be refreshing themselves very often. There was – and is – a lot to learn at Pluto, Charon, and Arrokoth.

But, Questions Remain

And, that was the point of a talk given by Dr. Alan Stern during AAS. He’s the principal investigator of the New Horizons mission. Based on findings made by the spacecraft so far, Alan brought a whole new set of challenges to AAS for astronomers and other scientists to consider.

For example, at Pluto, the mission discovered a nitrogen ice glacier on the surface. Turns out, it’s active. Why? What’s driving it?  The spacecraft also uncovered evidence for an ocean at Pluto. This world also has water ice mountains taller than the Rockies. There are materials called “tholins” on the surface of both Pluto and Charon and also mixed into the surface coloring of Arrokoth.

These discoveries raised a lot of questions that need to be answered with further laboratory work. In particular, why are surface ices darkening to the extent that they are?  Yes, the answer is something called “photolysis”, which describes nitrogen and other ices darkening in response to bombardment by far-ultraviolet (FUV) light. But, Pluto has an atmosphere that’s thick enough to interfere with the incoming FUV. So, how is this process still happening? As Alan pointed out, there needs to be more laboratory studies to understand the icy compounds that exist at Pluto and elsewhere on surfaces in the Kuiper Belt.

On Arrokoth, there’s a great deal of methanol on the surface, along with water ice and some other materials.  In essence, we need more information about those nitrogen, methane, and ammonia ices and their behaviors at this very low-temperature region of the solar system. Also, there are a lot of questions to be answered about the low-speed impacts that helped Arrokoth get its shape and its craters. Some of those questions can be answered in the lab, where people can measure the properties of these ices that exist out there, as well as the effects of cratering and other processes that act to change the surfaces of the worlds so far explored by New Horizons.

Understanding Past, Present, and Distant Kuipers

Understanding these objects and the how and why of their existence in the Kuiper Belt will give insight into the formation history of this region of the solar system. And, if other solar systems are like ours, knowing a bit more about our own Kuiper Belt will certainly help explain their formation and evolution history.

I talk about all of this and more in a video we recorded on the last day of AAS and put together by the California Academy of Sciences. Check it out (it’s on Facebook).  And, I’ll be presenting more stories from the AAS firehose over the next week or two. So, stay tuned for more from the firehose of astronomy!

Way back in 1989, we got our first good look at the planet Neptune when the Voyager 2 spacecraft did a quick reconnaissance flyby. Far from being a bland world like sister ice giant Uranus, Neptune was a bit more interesting. For one thing, it showed some interesting features called “dark spots” which turned out to be Neptune’s dark storms. There were other features in the upper atmosphere, but the Dark Spot and Dark Spot 2 really grabbed people’s attention. A few years later, Hubble Space Telescope took its first peek at the planet. By then, the storms had disappeared.

What happened? That’s a question planetary scientists have focused on ever since the flyby. And, since that time, several other similar types of features have come and gone in the Neptunian atmosphere. Hubble has been tracking those storms through a project called the Outer Planet Atmospheres Legacy (OPAL) program, in an effort to give more insight into these features.

These days there’s a relatively new storm in Neptune town, and it’s been around since at least 2018. That’s when Hubble took another look and found it. It was high in the northern hemisphere, and typical of such storms, it began drifting southward. In the past, when storms drift south, they tend to disappear. This latest storm could span the Atlantic Ocean if it occurred here on Earth.

Neptune’s Dark Storm Formation

What are these storms? They’re called dark vortices and are high-pressure systems that form, usually in the mid-latitudes. After a while, they drift toward the equatorial regions and start to lose stability. That’s because the Coriolis effect weakens the storm. Depending on the size and strength of the storm, it can withstand that effect for a while. Eventually, the storm just disintegrates. Storms that don’t end up in the equatorial region “kill zone” can remain stable for quite a while. Most of the storms that have been observed on Neptune follow the path to destruction. However, this latest one seems to be resisting the siren call of the equator.

Neptune’s Dark Storm Changes Course

This storm is acting differently. Instead of staying on a course south, it has turned back northwards. And, there’s another storm in the same general region. Is it a new storm? Or, did the 2018 storm spin off a clone? Those are the questions planetary scientists are looking to answer as they study this latest development.

It’s possible that as these storms head south toward dissolution, they tend to fragment and dissolve over time. Observers haven’t actually seen these disruptions in real time, so these two features give them a chance to see something happening more or less “in action” in the Neptunian atmosphere.

The mystery of how these storm features form still hasn’t been solved. Nor do planetary scientists have a strong feel for the structure of the storms. They ask “why are they ‘dark’?” It could be that there are high-altitude dark cloud layers. If that’s the case, then their existence could give a good insight into the vertical (top-to-bottom) structure of the storm itself. Perhaps there’s a more complex atmospheric chemistry answer. In any case, long-term studies, where the telescope studies the planets as often as possible, are the best way to understand the ephemeral nature of Neptune’s storms.