You may have heard recently that the Opportunity
Rover has not been in contact with the Earth since the 12th of June, 2018. This is due to a global dust storm which has
been covering the entirety of Mars for the last couple of months, during which the sun
has been blocked from reaching the solar panels of the rover. Opportunity is thought to have gone into safe
mode to preserve its battery, and with any luck it will reawaken now that the dust storm
has passed and that its batteries can be recharged. NASA has stated that they will give the rover
45 days from the 28th Aug to make contact with Earth, otherwise they will assume that
it is never going to recover. If that is the case, it will be the end of
a nearly 15 year mission, far surpassing the original mission timescale of 92 days. So what has it achieved during all that time
on Mars? Well unsurprisingly, it has contributed a
huge amount to our knowledge of the red planet, helping us understand the past of Mars, and
whether or not there was ever a surface water ocean on the planet. It has travelled more than any other vehicle
on an extra-terrestrial body. And it has helped shape our understanding
of the formation of the solar system. I’m Alex McColgan, and you’re watching
Astrum, and together we will take the journey Opportunity has taken on Mars. Let’s start right at the beginning. Having launched on a Delta II Heavy spacecraft,
Opportunity landed on the other side of Mars from its sister rover, Spirit, about three
weeks after Spirit had already landed. Opportunity used a parachute to slow itself
on its descent, and fired some rockets just before it landed. The effects of the rocket firing are evident
from this lighter patch of ground, as seen by the Mars Global Surveyor. Opportunity first bounced, and then came to
land inside a tiny 22m crater, now known as Eagle crater, with the heatshield and parachute
ending up a few hundred meters away. NASA scientists were so excited by this that
they called the landing a “hole-in-one”, although they weren’t actually aiming for
this crater. They didn’t even know it existed until they
got there, as Opportunity actually landed about 25 kms away from its intended target. As Opportunity emerged from its protective
shell, the first thing it did was have a look around. Opportunity is equipped with a panoramic camera,
which it can use to survey the area. It saw some outcrops only a few centimetres
tall, made up of extremely fine dust, each grain far smaller than the grains typically
found in Earth’s sandstone. Opportunity and Spirit were primarily on Mars
for its geology, the end goal being to see if Mars was ever a place that was conducive
to life. The way they did that was by looking at rocks
for evidence of water, thus giving scientists an idea of what Mars might have been like
millions of years ago, as rocks contain clues about their history. Opportunity explored the outcrop closely over
the course of the next few weeks, already discovering evidence that in the past some
kind of moving current had made the bedrock dip, although it wasn’t clear if it was
water that had done this, or volcanic flow or wind. You can see this in this image as the thin
rock layers are not parallel to each other. On Sol 30, or Opportunity’s 30th Martian
day on its surface, it got close to the outcrop and used its Rock Abrasion Tool to drill into
a section of the rock face. As it did so, it found something known to
geologists as “vugs” or voids in the rock, the result of crystals having been eroded
away. The rock also contained hydroxide ions, meaning
water was likely present when the rock formed. Next up for Opportunity was to dig a trench
in the soil for further analysis. It did this by digging its front wheels into
the soil while the back four wheels held it in place. After some shuffling about for 22 minutes,
it had made a trench 50 cm long and 10 cm deep. Under the top layer of soil were some things
it had not seen before, including shiny little pebbles and grains so small this microscopic
image can’t distinguish between them. Over the course of the few Martian weeks, having discovered everything it needed to,
Opportunity powered out of the crater at an average speed of 1cm per second, and headed
towards the next biggest crater in the vicinity, Endurance Crater, which is about 200m wide. On its way, it passed by this little tiny
crater called Fram. It took a photo, but didn’t stop for long. On Sol 84, it reached the edge, and had a
look inside. Mission planners already knew that Endurance
had many layers of rocks to be investigated, and wanted to have a closer look at them. Opportunity circled around the crater, looking
for a good entry point, as getting in wouldn’t be a problem, but getting out might. By Sol 127, mission planners decided to drive
Opportunity into the crater even if it couldn’t get out, as the value of the science that
could be garnered was too promising to pass up. So on Sol 131, it carefully edged its way
over the ridge of the crater, and tried to reverse back to see if it could. Luckily, the angle of the rim was only 18
degrees, well within Opportunity’s known safety margin, so the excursion into the crater
began in earnest. Opportunity went on to spend 180 Sols in the
crater. It explored an area called Karatepe where
it saw various layers in the bedrock. It went near to, but not into some sand dunes
as mission planners didn’t want it to get stuck. It saw some wispy clouds similar to Earth’s
cirrus clouds. And lastly, it went to a cliff face called
Burns cliff, an impressive looking cliff face with various layers separated by broken up
rocks and dust. It finally left Endurance on Sol 315. During the time there, the data collected
by Opportunity meant that scientists were able to confirm that water didn’t just cover
this area once, but it was in fact episodic in nature, with floods that would have washed
across this landscape before drying up again. At any rate, the water here would have never
been that deep. After that substantial discovery, the next
stop on its adventure was to investigate out its own heat shield. On the way, it came across a rock that was
later confirmed to be a meteorite, named Heat Shield Rock. It was the first meteorite to be identified
on another planet. Opportunity then set a course for Erebus crater, It pressed ahead through a region called the
“etched terrain” to search for more bedrock. While traversing this area, on Sol 445, Opportunity
got stuck in a 30cm sand dune. Thing did not look good for the rover; all
four of its corner wheels were dug in to the dune by more than a wheel radius. This dune came to be known as “Purgatory
Dune”. It stayed motionless for just short of 20
Martian days as mission planners frantically tried to figure out how to get it out. They simulated the scenario on Earth and tried
various methods before they ordered Opportunity to try anything. On Sol 461, the rover advanced a few centimetres
to see if it was doing what their tests had predicted. Over the course of the next 20 Martian days,
Opportunity moved a few centimetres, took a photo of the progress, and sent the results
back to mission control. By Sol 483, Opportunity had successfully escaped
the dune and all six wheels were on firmer ground. It would have been disappointing if it had
travelled for a year on Mars, just to get stuck by a 30cm dune. Opportunity studied Purgatory dune for another
12 Martian days, before setting off again on its way to Erebus crater. By the time Opportunity reached Erebus, it
had received new software to prevent it from getting stuck again, with software designed
by learning what happened from the experience at Purgatory. With this new software update, it was ready to carry on its adventure at Erebus crater. Which we will save for the next part! Did you enjoy learning about Opportunity today? The pictures that it took are awe inspiring,
but as I mentioned before, the main reason it was there was to perform experiments and
gather valuable data to further our understanding of Mars. But what is the process of making scientific
discoveries? Brilliant.org has a great course on the fundamentals
of science, and how we attain and organise knowledge in order to better understand the
universe around us. With courses like these, you will gain a much
better understanding and context of science! This context is hugely valuable when learning
about our universe. So give Brilliant a go for free today! By using the link brilliant.org/Astrum, you
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