A chain of Mars exploration catastrophes: When NASA confused the metric with the imperial system
The 1990s were a disastrous decade for Mars exploration projects. Out of seven attempts, only two were successful. And the apparent ease of Viking 1 and 2 — a pair of NASA landers and orbiters — hid a more difficult reality: landing on the red planet was much more difficult than it seemed. In the first 50 years of exploring Mars, almost half of the vehicles sent there crashed or stopped working.
In September 1992, NASA launched its Mars Observer, a platform that was meant to continue and expand the studies carried out by the Viking orbiters. It was a newly-designed vehicle, the first of a class intended to make planetary visits not only to Mars, but also — in the future and with the necessary adaptations — to Venus, or even Mercury.
It was built from a standard structure typical of conventional communications satellites. It seemed like a good idea from the point of view of taking advantage of already proven designs, but in the end, it wasn’t. Some of its components — which had worked well for weeks around the Earth — wouldn’t be able to withstand the rigors of a months-long trip to much colder environments.
When the Mars Observer was only a couple of days away from reaching its target, it was given the order to pressurize its tanks in preparation for braking. It’s unclear exactly what happened: suspicion points to a slight leak of oxidizer (nitrogen tetroxide) from a valve. Even though it was a small amount over the course of an 11-month-long flight, the corrosive liquid would have built up in the pipes. Hence, when a second set of valves opened, it could have come into contact with the fuel, causing an explosion. This is just one of several hypotheses, but the sudden failure of communications didn’t allow for a definitive conclusion to be reached.
