I spent about twenty minutes of my lunch break on Monday hunched over my laptop at the kitchen table, half a sandwich going stale next to the keyboard, watching NASA TV's livestream buffer and unbuffer while a room full of people at JPL either cheered or held their breath. That was the InSight landing. By now you've read fifty posts about it (Mars, a lander, seven minutes of terror, all of it), so I'm not going to redo that whole play by play. What I keep thinking about three days later isn't the lander at all. Its the two little satellites that tagged along and nobody talks about.
They're called MarCO-A and MarCO-B, and JPL engineers nicknamed them WALL-E and EVE, which is objectively a good bit. Each one is a cubesat, roughly the size of a briefcase, about 24 by 36 by 11 centimeters folded up, with solar panels that unfold once they're in space. They launched back in May alongside InSight on the same Atlas V rocket, then flew along on their own trajectory the whole way to Mars, about 300 million miles, on a total mission budget somewhere around $18.5 million for the pair. For context, that is roughly what one 30-second Super Bowl ad cost that year.
Their entire job was to be there for those seven minutes. When InSight hit the Martian atmosphere and started its descent, it couldn't talk directly to Earth in real time, the geometry doesn't allow it and the old relay orbiters weren't positioned right for a live feed. So MarCO-A and B flew past Mars at exactly the right moment and relayed InSight's status tones back to Earth almost live, maybe an eight-minute delay for the radio signal to cross the gap. That's how the control room at JPL knew "touchdown confirmed" within minutes instead of having to wait hours for an orbiter to swing back around and dump its recorded data. Without them, everyone in that room, and everyone like me watching a stream at their kitchen table, would've spent the afternoon just sort of guessing.
The part that gets me is that this was the first time anyone had used cubesats past low Earth orbit at all. These things are normally the kind of hardware a university club builds for a few hundred thousand dollars to test out a sensor in orbit for a semester. Sending a pair of them 300 million miles to relay a signal, using off-the-shelf-ish parts and a cold gas thruster system for course correction, is the kind of decision that sounds insane until it works, and then everyone acts like it was obvious the whole time. It wasn't obvious. It was a gamble that paid off in front of an audience.
I'll admit my opinion here is a little contrarian: I think the InSight lander itself, cool as the seismometer and the heat probe are, is going to produce years of slow, patient, unglamorous science that's genuinely important but not exactly thrilling to read about week to week. The MarCOs already did their thrilling part and they did it in one afternoon. After the flyby they kept transmitting for a bit (I think one of them got some nice parting shots of Mars with its own tiny camera) but their mission was basically done the moment InSight's wheels, or legs I guess, touched dirt. That's a strange kind of career. Peak relevance for about twenty minutes, then quietly drifting off into a solar orbit forever.
Also, unrelated complaint: the NASA TV stream kept dropping to potato quality right at the tense parts, which felt like a cruel joke given how much money and how many years went into getting to that exact seven minutes. I ended up half-watching Twitter for confirmation because the video froze right as the parachute was supposed to deploy. Somebody should fix that for the next one, whenever that is.
Anyway. Next time somebody tells you a satellite has to be big to matter, mention the two briefcases that beat the deep space network to the punch.