Back when I was a beginning science writer, I had the great fortune to cover the Voyager 2/Saturn flyby mission. The spacecraft (and its sister craft Voyager 1) met many challenges during their 12-year trip to explore the giant planets of the outer solar system. After they left the planets behind, both Voyagers embarked on the next phase: getting out of the solar system and into interstellar space.

Today, they’re “doing” the Voyager Interstellar Mission. Both spacecraft are outside of the solar heliosphere now. For the foreseeable future, they will transit the outer Kuiper Belt and Oort Cloud. Currently, the spacecraft transmit intermittent messages that convey data about the conditions they encounter. They’ll do that until their transmitters stop or they run out of power sometime in the next decade or so.

A Message in a Bottle

In 20,000 years, the Voyagers will be free of any possible influence of the solar system. That’s when they will commence the final part of their mission: as messages in a bottle. For the next millions or billions of years, they’ll traverse the galaxy in a sun-like orbit. They’ll orbit the center of the galaxy (just as the Sun does). And, they may get found by other life forms. Maybe.

If that happens, and those beings wonder where the Voyagers came from, and who created them, each spacecraft contains information about its creators. How did that information get there? Scientists on the Voyager teams, led by the late Dr. Carl Sagan, created a “message in a bottle”.

It’s called the Voyager Gold Record and both have encoded on them the sounds and images of Earth. Each Voyager has one attached to its spacecraft “bus.” Protective covers protect the records. Engravings on the covers give information about how to play the records. They tell the location of Earth, what humans look like, and give some rudimentary science and mathematical symbols.

Each of the two spacecraft is on trajectories that will take them on voyages through the galaxy for as long as they last. They won’t pass too close to stars, but they may experience interstellar clouds of gas and dust during their journeys. And, in the far distant future, they could ride out the collisions of our Milky Way and Andromeda, and interactions with the Magellanic Clouds.

Will the Bottles Survive?

Those lengthy trips through the future of our galaxy caught the attention of scientist and grad student Nick Oberg. He presented a paper at the recent AAS meeting about the futures of the two Voyager spacecraft. Essentially, he asked: what will happen to the spacecraft and will the records survive? The short answer is, of course, they could survive. However, we have no way of knowing for sure that they WILL. But, we can make some predictions.

Here’s Nick’s scenario: as mentioned above, in about 20,000 years, the Voyagers will exit the Oort cloud. Voyager 1 is on a trajectory that takes it slightly above the plane of the Milky Way. It will travel within a region where the star density is about half of what it is here by the Sun. However, the spacecraft could encounter molecular clouds and be bombarded with microparticles. If so, then the steady bombardment could erode the outside cover, but the record itself would probably be okay. Voyager 2 is on a trajectory that keeps it within the plane of the solar system. There’s some chance it could encounter some fairly thick clouds of interstellar gas and dust. Passage through the clouds could subject the covers to the bombardment by microparticles. If the bombardment is severe enough, the cover could experience more erosion. It might get breached and the record might sustain damage (or be completely destroyed).

The Voyagers’ Far Future

Assuming both Voyagers aren’t picked up by interstellar junk collectors or have collided with a rogue asteroid, both of them will ride out the collision of the Milky Way and Andromeda. They could also be silent witnesses to the interactions of our galaxy with the Large and Small Magellanic Clouds. As a result of the shock waves and other events that go along with galaxy mergers, the Voyager spacecraft would likely be flung into different orbits. They’d be moving much farther out than they are now.

Depending on whether they stay in the “new” Milkdromeda Galaxy, or if they’re tossed out to intergalactic space, the spacecraft will experience more cosmic ray damage. They could glide through clouds of thin, hot, intergalactic gases. But, they won’t be completely alone. They’d still be part of the Local Group of galaxies. Now, if that collection merges billions and billions of years from now, our spacecraft could end up orbiting a very old, very massive elliptical galaxy. That would be something like a hundred thousand trillion years from now.

It’s a lot to think about for our spidery little spacecraft. Long after our star has gone to red giant and become a white dwarf, and our planet is gone, there’ll still be two little messages in bottles out there. If their records survive, they’ll be the only proof that our planet existed and that a rich variety of life lived on its surface. Somebody, somewhere in the far distant figure will look at the craft — and maybe figure out how to play the records. And, the sounds and images of our time in the universe will unfold before their sensors, reliving of our existence on Earth.

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!