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Before every Mars landing there is a tense period of radio silence between the moment the space craft hurtles into the atmosphere and the moment it touches down. During what is now know as the seven minutes of terror, the spacecraft slows from several kilometers per second to a complete stop, all on its own.

These days scientists have the help of sophisticated computers, A.I., and fancy gadgets like self-piloting sky cranes. But back when scientists made the first successful landing on Mars, those minutes of silence were especially terrifying.

That first landing didn't earn a big place in history books and yet the strategy behind it paved the way for many truly historic missions to Mars. This was all back in May of 1971 when soviets launched the Mars 3 mission, which included a lander and an orbiter. It launched just days after its twin, Mars 2, and set off on the six month journey to Mars.

The plan was for the orbiters to take photos of the Martian surface from on high and return information about things like topography and magnetic fields. They'd also relay communications from the landers to earth. Meanwhile, the landers would take pictures from the surface, and measure properties like wind speed, air pressure, and temperature. They even contained an itty, bitty rover on skis that would study the soil.

That might all sound like a tall order, considering that at this point the Soviet Union hadn't even done a flyby of Mars. But they had done some similar science on the moon, so these types of experiments weren't entirely new. 

The part that was new was the landing, and landing on Mars is not easy. The first problem is that its atmosphere is super thin. Spacecrafts are travelling several kilometers a second when they arrive, so they need to slow down a lot. But a parachute isn't that effective when it doesn't have a lot of air to grab onto. Unfortunately, the atmosphere is also still thick enough that the spacecraft will burn up if they're not carefully protected.

And the whole descent has to happen automatically, because a spacecraft gets all the way to the ground faster than a single signal can travel from earth. So it's all on its own. And if the slightest thing goes wrong, a Mars landing can be doomed. That's what happened to Mars 2. Mars 2 entered the atmosphere at too steep of an angle and plunged straight into the surface. But it did earn the honor of being the first spacecraft to reach the surface of Mars, technically. And a few days later its twin became the first to stick the landing.

Mars 3 got off to a better start. After it split ways with its orbiter, it entered the atmosphere at a super shallow angle, less than 10 degrees. That made it possible for Mars 3 to take advantage of a technique called aerobraking. Basically, it used the drag from the atmosphere to help it slow down. Then it deployed two parachutes, starting with a small pilot chute, then a larger main chute. The main chute would tear if it opened too soon, so at first a cord around the base kept it from fully inflating, in a technique called reefing. Then, once it got below supersonic speeds, it popped open.

At this point, the altimeter turned on. That's a tool that uses light to calculate distance by bouncing radar signals off the ground and measuring their return time. And using this, the descent module could kick off its final landing sequence, right before it hit the ground. By then, it was still going more than 60 meters per second. So, a split-second away from disaster, it tossed off its parachute and fired its retrorockets. Even so, it slammed into the ground at more than 20 meters per second, or about 45 miles per hour. But, it was designed to. Shock absorbers inside protected the cargo, and when everything came to a stop, four petal-like hatches opened to reveal the lander.

Unfortunately, it only transmitted for 20 seconds, and sent back a grand total of one grainy image. As far as we can tell, it had the misfortune of landing in a severe dust storm, and that may have done it in. So Mars 3 never really went down in history, but in a lot of ways it was an important success. For one, the orbiter sent back pictures of the surface, revealing huge Martian mountains and providing the data for topographical maps. And it collected data about the atmosphere, gravity, and magnetic fields of the red planet.

But the lander was important too. Not only did it mark a milestone and prove that we could land on Mars, it taught us how. It showed us how a bunch of sophisticated automatic maneuvers could be combined to pull off a pretty soft landing. And while it's not simple, this sequence of steps replaced the need for lots of heavy fuel, and other landing gear that might overburden the craft.

These days, the basic steps for landing on Mars are mostly the same. Recent missions also used aerobraking, parachutes, retrorockets, and radar to make their way to the surface. The main difference is that, as payloads have gotten heavier, engineers have designed bundles of airbags and elaborate sky cranes to assist with the final touchdown.

By now, humans have pulled off Mars landings 10 different times in the last half-century. And while Mars 3 didn't give us glamorous photos or discoveries to remember it by, its success is embedded in every single mission that comes after it.

And that's why we've decided to immortalize this little Mars lander that sort of could. That's right, Mars 3 is May's pin of the month. Right now, you can own this little guy if you follow the link in the description. We'll take preorders throughout the month, and we'll ship them after that. But we'll never make any more of this pin again. Instead, next month there will be a new space pin for you to enjoy. So check it out in the link below, and thanks for your support.

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