If you’ve read even a smattering of the posts on this site, you know the Parallax Machine is a fan of math. The certainty of math, combined with the incredible way in which it allows us to approximate how the world around us works, makes it a powerful tool. It even makes what might seem like the impossible not just possible, but probable, as long as you follow the instructions.
Nowhere is the power of math more resoundingly demonstrated than when we safely land a robot on another world. The closest Mars ever gets to Earth is over 30 million miles away. Earth is orbiting the Sun at 67 thousand miles per hour, and Mars at 54 thousand miles per hour. And yet, in July and September of 1976, we landed two probes at different locations on the surface of Mars, almost a year after each one was launched, both of which operated for several years afterward to tell us what they found there. Mathematics allows us to do anything when we put our minds to it.
These were the Viking missions to Mars, and they actually consisted of two parts each – an orbiter and a lander – with both elements collecting multiple years of valuable data. The Viking 1 and Viking 2 landers were the first U.S. spacecraft ever to land on another planet. One of their principle activities was to collect soil samples for analysis to determine if any life existed there. This was the endgame for the century of speculation about life on Mars that preceded the Viking missions. And while Viking 1 and Viking 2 each only examined one spot on the red planet, neither one found any evidence of life.
Most people in America are familiar with the space race between the United States and the Soviet Union that ultimately landed humans on the Moon in 1969. But all during that same time period, there was a similar space race to Mars – littered with early failures. The first five attempts were all by the Soviets; four of them suffered launch failures, and the fifth lost communications before it arrived at Mars. The first U.S. attempt also failed, but in 1965, the American spacecraft Mariner 4 was the first to successfully fly by Mars – four years before Neil Armstrong’s giant leap for mankind. The Soviets were the first to successfully land on Mars, with the Mars 3 lander in 1971. Unfortunately, communications contact only lasted 14.5 seconds after that. All told, the majority of Mars missions before the Vikings were failures in one way or another, which makes the resounding success of the Viking missions that much more impressive.
Getting to Mars continued to be difficult even after the Viking missions. The next attempts were by the Soviets in 1988 with their Phobos missions (named after one of Mars’ moons), of which only one orbiter was successful. The next U.S. attempt – the Mars Observer mission of 1992 – lost communications before entering orbit. But then three U.S. missions launched in late 1996 seemed to turn the tide – at least enough to make us keep trying. Mars Global Surveyor orbited the red planet for seven years. Mars Pathfinder landed successfully on the Fourth of July in 1997 and gathered data for a couple of months afterward. And Sojourner capped it all off as the first successful rover dispatched to another planet, puttering around for 84 days before falling silent.
As if to remind us of the dangers of hubris, the next few years brought more heartache. Mars Climate Observer burned up in the Mars atmosphere – a trajectory error resulting from the use of incorrect units in the software, and a reminder that math always requires us to follow the instructions. Mars Polar Lander got there but failed to… well,… land. But in the early 2000’s we rebounded again – the U.S. and the European Union launched the very successful Mars Odyssey and Mars Express missions, respectively – both of which are expected to continue operating for several more years from *today*.
And then came two missions – Spirit and Opportunity – which may have permanently turned the tide for Mars exploration. Both of these rovers landed on Mars in January 2004, and both of them were phenomenal successes. They were only designed to last 90 days, but Spirit survived until 2010, and Opportunity sent its last signal back to Earth in 2018 – having survived 60 times longer than originally planned. In between, a number of other successful missions to Mars have been launched – but my favorite of all these was Curiosity, which was launched in November of 2011, and landed in August of 2012 – less than one and a half miles from its target, by the way. I feel lucky if either Apple or Google Maps get me that close to where I want to go.
The Curiosity rover is still operating today. But equally amazing are the NASA-named “7 minutes of terror” that accompanied its landing. NASA JPL has a terrific infographic summarizing the whole process at this link: https://www.jpl.nasa.gov/infographics/infographic.view.php?id=10776. For those of you with lazy hyperlink fingers, I’ll summarize it in words here. Curiosity approached Mars at 13,000 miles per hour (about a quarter of the speed at which Mars orbits the Sun). As it approached and entered the Martian atmosphere, Curiosity had to be decelerated to around a thousand miles an hour. It then deployed an enormous parachute while still descending at 900 miles an hour. The heat shield separated from the plummeting spacecraft while it was still traveling at 370 miles an hour. After the parachute and reverse rockets stabilized the descent down to 70 miles an hour, rocket boosters fired to slow the descent further while a sky crane lowered the rover down at 2 miles an hour. Hanging 25 feet from its mother spacecraft, the rover then touched down softly, waited a couple of seconds to confirm it was on solid ground, and then issued a command to cut the bridles. The spacecraft then fired its boosters one last time to ensure it landed (okay, crashed) sufficiently far from the rover to avoid endangering the rest of the mission. From the top of the atmosphere to the surface of Mars took seven minutes – on par with the time it takes for communications to get from Mars to Earth – and everyone had to wait until the rover sent its first signal back from the surface to find out if it worked. I was watching NASA TV and waiting right along with them (as were millions of other nerds). I actually cried a little. Best reality show *ever*.
Many more missions are in work or en route to Mars – with more nations getting involved as we go. But the tsunami of science data that started in full force with the Viking missions has revolutionized our understanding of Mars already. We’ll take a look at some of what we have found in the next post. But as with all things in life, sometimes it’s not about the destination – it’s about the journey.