Alex Gizis: Could you do a version of Starlink around Mars? No, that's going to be a problem. And you cannot get an Internet connection to go all the way to Mars. Elon Musk needs something else to help him.

Ryan: So how does that work?

Alex Gizis: Well, Vinton Cerf, you'll remember, as one of the original inventors of the Internet, has been working for the last few years on the interplanetary network. It is his vision that people, including NASA, have bought into of building a new network of networks and networks.

So this is the network that will connect all the planets and all the spaceships in the solar system together into one new interplanetary network. The concept is each planet gets an Internet. There'll be an Internet on Earth, which is the Internet we know, and there'll be a Mars net, which is a copy of the Internet, basically running on Mars.

Different domain names and a lot of the same IP addresses being used because it's a different Internet, you can do that. Jupiter and its moons will get one. Generally, I think, they think each of the moons will be on the same one as the planet it's circling. But, separate. Connected together by this thing called the Interplanetary Network (IPN).

The Interplanetary Network, because the time between the planets is minutes, or even hours, as you start getting further and further away, the time gets longer and longer to be a light. And if you're trying to do a round trip, it's all doubled, right? So Mars at its closest comes within about three minutes of Earth, which means you can say, "Are you there?" / "Yes." - it'll take six minutes.

At its furthest on the other side of the sun, it's 12 minutes away.

Ryan: But is that straight through the Sun?

Alex Gizis: Well, it would be straight through the Sun. And so IPN even takes care of that. If you have enough probes and spaceships and planets and stuff. IPN will realize the Sun's in the way of Mars, so it'll send the message to Jupiter first and then Jupiter can send it because there's a triangle going on here and it can make it around the Sun.

All this adds time, obviously sending a message all the way to Jupiter, and then all the way to the other side of the Sun. This is a significant time. But it's less time than waiting for Mars to go further in its orbit. Everything takes time.

Ryan: So is this just a hypothetical technology, or is it actually in use?

Alex Gizis: No, they've started using it. They call it the bundle protocol, and they've been using it on a lot of the Mars probes that they've sent in the last few years.

They're actually using the IPN, Interplanetary Network, using these bundled protocols to talk to them. That's how they're downloading the pictures and stuff. And there are some applications on Earth. It turns out, when you start sending these robots deep underwater, you start running into almost the same issues.

Very hard to reach them, very low bandwidth at the bottom of the ocean. And the speed of light isn't as high, but there's just tough communications issues. So some of those underwater operations have started using bundle protocol as well.

And there are some other funny applications, including tracking reindeer in Sweden. They put these little tags on them that are very low battery. They try to bundle up the information and send it, and they're using the same protocols.

And there have been neat experiments. Like, they had the guys in the International Space Station, the astronauts there, control a robot in Germany. It's actually beaming down from space to control a robot, which is a tricky little thing when you're overhead.

But without the bundled protocol, it would be nearly impossible. When the International Space Station is on the other side of the Earth. So they bounce the bundles all the way around the earth so they can control the robot the whole time. And it works. They tested it.

Ryan: So how do they bounce that data?

Alex Gizis: There are other nodes, you have to have other satellites and things or base stations on the ground that can say, "yeah, I think I can get it to that guy" and they'll accept the bundle. And once they get it, they send it on either to the destination or to the next guy who thinks he can get it there, like the mail.

Ryan: But is it just radio or?

Alex Gizis: Yeah, typically it's radio. All the communications to Mars these days are the deep space network. It's three huge satellite dishes that they'll point at Mars, right? This is how, you know, the probes on Mars have these little radios. You ever wonder how do they get a signal all the way back to Earth?

The answer is it's a little radio and a huge dish on Earth. Three huge dishes all pointed. They're trying to pick up the same signal. And that's how they pick up enough to get it really working. There are other ways to do it though, like lasers. NASA did a cool experiment where they put mirrors on the moon and then bounced signals with a laser off and back, and they got a 622 Mbps link.

But the thing is, the latency of the link is two and a half seconds. And this is where you start seeing that Internet protocols are not meant for space. TCP, you know, the main transport protocol for the Internet, gets slower and slower the worse the latency is. And it turns out that if you have 2.5 seconds of latency on your link, the top possible speed for TCP is 80 Kbps.

Even though the link is 622 Mbps. TCP, what it does, it sends a bunch of messages and then waits to hear that you got them. And that's the problem. So the link ends up sitting empty because TCP can't imagine that it's supposed to send 622 Mbps times two and a half. That's supposed to send gigabits off without even waiting for a response.

It can't do that. That's outside the bounds of what they thought of the protocol. So it ends out an 80 Kbps link if you run regular Internet protocols over it.

Ryan: So is Starlink using any of this technology?

Alex Gizis: Not for the Starlink satellites. Those are in low Earth orbit. It's a few milliseconds to get a message to them, a few milliseconds for it to come back. So they can just use standard Internet protocol.

Now more and more, of course, SpaceX is talking about putting things on the Moon, putting things in deep orbit, putting things on Mars, and You basically discover once you get past the Moon, it's impossible to use Internet protocol anymore. So yeah, they'll, they'll be using bundled protocol for anything that goes beyond that.

Ryan: Okay, so going back to the Twitter thing. Right. How would people on Earth Twitter be able to see Mars tweets?

Alex Gizis: So what would have to happen is you would run a Twitter on Mars. You would have a Twitter server there. People on Mars would check there for tweets and post their tweets there back and forth. And then you would have a sort of gateway, a bridge between the two that runs on each side, pulls together a bunch of tweets, makes them into a bundle, and then ships them across. And when they finally make it to the other server, you take apart the bundle, you take the tweets, and the server would pretend that all these tweets were just tweeted. Now, there's not going to be enough bandwidth between Earth and Mars, ever, to send all the tweets back and forth.

So there'll have to be some smarts saying, you know, which people are actually being followed by the people on Mars, grab their tweets. One of the most popular tweets in the world, we'll grab those, and put those together into a bundle. That you could ship across. So an interesting sampling of Earth's tweets being into Mars.

And then the same thing on Mars. They gather together some tweets from there and send them. Conversations are going to be hard, right? When you see a tweet appear, the person didn't just tweet it. It was probably a while ago if they were on the other planet.

Ryan: So you could just get a sampling of 200 Elon Musk tweets from the past 24 hours.

Alex Gizis: The dream, right? I actually, at one point, sort of designed a bunch of this for Mastodon. I was thinking, if there's a Mastodon server on Mars, how do we do this? I designed some. I didn't get very far with the software. I ended up having an interesting discussion with people. I announced on Mastodon I was thinking about doing this.

All these people had tips and tricks and pointing me at the right documentation. I think I could have done it except, of course, that there is no Mastodon on Mars.

Ryan: Not a lot of demand for that yet.