Although the “Countdown to Curiosity” articles detailed all of Curiosity’s amazing scientific apparatus, the articles didn’t really put into perspective how much better Curiosity is than the other Mars rovers (Sojourner, Spirit and Opportunity). So let’s right that wrong!
Sojourner landed way back in December 1996! I was actually studying for my PhD at the time, but there was a lot of great press coverage. It was perhaps the first space mission to really use the internet effectively. But for all the communication successes, Sojourner didn’t really have a great suite of scientific instruments. Given it’s small size, just a little over 10 kg and only 60 cm long, there wasn’t all that much space for scientific payloads. The key scientific instrument (other than cameras) was an Alpha Particle X-ray Spectrometer for determining the elements in rocks (Curiosity has a much more advanced one). But what many people remember about Sojourner was how slow it moved: it had a top speed of a little over 0.5 cm a second! But there again, this mission was put together on one tenth the budget of Curiosity.
The twin Spirit and Opportunity rovers came next, landing in January 2004. Like Sojourner, they both carried an APXS, but this time they came with more sophisticated spectrometers to make even better assessments of the precise elemental components of the Martian rocks and minerals. Much larger in size, at 185 kg and around 1.6 metres long, they were much more capable of carrying a heavy payload. They also had the advantage of a robotic arm so they could get in close and even abraid the surface of rocks to see what was lying underneath (the RAT tool!) But perhaps what everyone remembers about Spirit and Opportunity was their “Energizer Bunny” impressions – they just kept going and going! With it’s solar cells still operational, Opportunity is still working today after having covered almost 22 miles! Spirit got stuck in a dusty soil area in 2009 and unfortunately sent its last communication on 2010.
Fast forward to today’s super-rover: Curiosity! Now we’re talking about a 900 kg vehicle roaming about, which is capable of carrying half the total mass of Spirit in scientific experiments alone! NASA likes to use the analogy that Curiosity is about the same size as a Mini-Cooper. In terms of the scientific experiments, the list is pretty amazing (Curiosity is the first rover with a laser): ChemCam (remote sensing, including the laser, for chemistry) APXS, ChemMin (for mineraology and chemistry), SAM (detailed sample analysis), RAD (radiation assessment), DAN (for detecting ice near the surface), REMS (for monitoring Martian weather) and not to mention a whole bunch of cameras! All in all, Curiosity is leaps ahead of went before it! It should truly help us understand the Martian geology and mineralogy in unprecedented detail.
Hopefully, that makes it clear why Curiosity is so important for studying Mars. It’s scientific designation, “Mars Science Laboratory” puts into perspective what this mission represents – a true suite of lab experiments on the surface of Mars!
And one last image to leave you with – a shot of all three rovers compared (but not on Mars!)