The Opportunity Rover has now come to the
end of a very successful mission on Mars, spending over 15 years operating on its surface. Being that long on another planet means it
has made a lot of fascinating discoveries and it has a lot of stories to tell about
its adventure. In the previous episodes, Opportunity visited
various craters, drilling into rocks to see into Mars’ past. It got stuck in sand dunes, but got itself
out thanks to the ingenuity and patience of the mission control team on Earth. Opportunity also experienced a few mechanical
problems, meaning its arm can’t be stowed any more. But even with all these hinderances and successes,
this series isn’t even halfway through its mission yet! I’m Alex McColgan, and you’re watching
Astrum, and together we will follow the tracks of Opportunity, and experience what it saw
and discovered on the Martian surface. We left off last time around Sol 1700, or
the 1700th Martian day of Opportunity’s mission, which equates to about 4 and a half
Earth years. Opportunity had just finished exploring the
Victoria crater, an impressive 750m wide crater with layered cliff faces and exposed bedrock. It was by far the biggest crater Opportunity
had visited yet, but after a successful excursion around Victoria, mission controllers had their
eyes set on a much bigger fish. This is Endeavour crater, a huge but shallow
crater at 22km across and 300m deep. But why Endeavour crater? Due to the distances involved, it would take
a long time for Opportunity to get there, so, what’s special about this place compared
to anything Opportunity had seen before? The most compelling reason, and indeed one
of the science goals of Opportunity, was to find evidence of past oceans on Mars. At this point in 2008, the theory that Mars
once held an ocean on its surface was only just starting to get solid evidence thanks
to the Spirit and Opportunity rovers. Opportunity at this point had discovered that
water once existed on the places it had visited, but these places were no more than shallow
flood plains which dried up periodically, not a true ocean. On the other hand, the Mars Reconnaissance
Orbiter had spotted what was believed to be clays around Endeavour crater, clays being
hydrated minerals which could have only formed from water being on the surface for extended
periods there. Could Endeavour have been part of a more permanent
ocean? And if there really was a surface ocean, are
there clues to indicate that could it have harboured life? Mission controllers had to find out. And so Opportunity left Victoria crater and
began its arduous journey south. The mission team were determined to reach
their destination as quickly as possible, while also keeping a look out for anything
of interest along the way. Opportunity made good time across the Meridiani
plains, and by sol 1818 it had travelled more than 3km. Nothing noteworthy really happened until sol
1947, where a large rock was spotted. The mission team decided to investigate, discovering
that it was a meteorite which they named ‘Block Island’. In fact, large rocks seemed to be the only
thing to keep Opportunity busy, later spotting another one named ‘Shelter Island’, and
a third called ‘Marquette Island’. Marquette Island was of particular interest
to scientists though, as they believed this rock was part of the ejecta from a large meteor
impact, meaning this rock would have come from deep in Mars’ crust. Scientists could tell because the grains within
the rock are coarse with a basalt composition. The coarseness indicates it cooled slowly
from molten rock, allowing crystals time to grow. Had it formed near the surface, the crystals
within it would have been a lot smaller as it would have cooled a lot quicker. Opportunity was never alone on Mars. It had a sister rover named Spirit, which
was exploring the other side of the planet at the same time. They both landed on Mars at roughly the same
time, and had both far exceeded their original expected life span of 90 sols, at this point
they were 1900 sols into the mission. Although, just like Opportunity up until this
point, Spirit had encountered some mechanical failures too. Most notably, one of its front wheels jammed
only 700 sols into its mission, meaning it dragged this wheel along as it travelled. In a way, I almost think Spirit was NASA’s
darling between the two rovers, Spirit often got more media attention for the things it
was discovering on the planet. However, it was around the time Opportunity
explored those rocks that Spirit, on the other side of the planet, attempted to drive over
a sand dune and got its wheels stuck deeply in the sand. Spirit’s operators began the long process
of attempting to get it unstuck through simulations and testing on Earth based replicas. Meanwhile, Opportunity carried on its long
journey to Endeavour. By Sol 2138, Opportunity finally reached a
landmark of note, Concepción crater. It is only 10m wide, but probably the youngest
crater visited yet, evidenced by the exposed rubble and ejecta. Nothing particularly new was found there compared
to any of the bedrock Opportunity has examined in the past, which was simply sulphate rich
sandstone containing peppercorn size spheres, known as blueberries. At least the crater provided a contrast to
the vast expanse of rolling sand dunes. Eight months had passed since Spirit got stuck
in the dune. The sand that enveloped its wheels was particularly
fine, and the process of excavating Spirit was exasperated by its jammed wheel. During this recovery process, another of Spirit’s
wheels jammed, meaning only 4 of the 6 now worked. The Martian winter approached for Spirit,
and it was getting less and less sunlight to power its batteries, until finally, a low
power fault occurred on the rover, and its systems disconnected from the battery. Spirit went silent. Mission controllers attempted for months afterwards
to regain contact with the rover, but NASA eventually called an end to Spirit’s mission. For the first time since it landed, Opportunity
was now alone on Mars. Opportunity’s long slog over kilometres
of sand dunes to reach Endeavour was becoming taxing for the rover. Perhaps overly anxious not to have a repeat
of what happened to Spirit, mission controllers decided to reroute Opportunity’s course,
a longer route but hopefully a less arduous one. This route would also take it by what was
named Santa Maria crater. By sol 2244, Opportunity set a new record
for the longest lasting mission on Mars, finally beating Viking I’s mission duration. Opportunity could begin to see the rim of
Endeavour, spotting the landmarks of Cape Tribulation, Cape Byron and Cape Dromedary. However, even 100 sols later, it was only
halfway to Endeavour from Victoria. It had made good time, considering it has
a top speed of 5cm per second, and often went half of that to be safe, with frequent stops
to look out for potentially problematic sand dunes. You’ll notice the rover’s tracks are ahead
of the rover in this time lapse. This is because there is also a navigational
camera on the back of Opportunity, allowing it to drive forwards or in reverse to evenly
distribute wear and tear on the motors. Although, another reason right now was to
protect Opportunity’s extended arm, which as I mentioned in the last episode, got stuck
in this position. On sol 2449, Opportunity finally arrived at
Santa Maria crater. It’s a 90-meter-wide crater, and was important
to mission controllers as there was already evidence here of hydrated sulphate minerals. As I mentioned, hydrated minerals can only
form under bodies of water over extended periods of time, so this was an exciting precursor
to what they wanted to really investigate around Endeavour, which was still a tantalising
two-year journey away. Opportunity also stopped here to take a spectacular
time lapse of a Martian sunset or two, with one of the time lapses showing a transit of
Mars biggest moon Phobos across the Sun. Over two Earth years had passed in just this
one episode. Opportunity had soldiered on well beyond its
expected mission lifetime of 90 sols, and even outlived its sister rover Spirit. It and the mission team had earned a rest
at Santa Maria, and they all spent three months happily examining rocks and unlocking secrets
about the history of Mars. After that, it was onward and upwards for
Opportunity towards Spirit Point, a point around the rim of Endeavour, an inspiring
commemoration of the mission’s loss on the other side of the planet. And we will save this journey for the next
episode! Every day, Brilliant publishes Daily Challenges
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20% off their annual Premium subscription. Thanks for watching! Find the episode playlist for this mission
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