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You join us during the final days of the 
Spirit rover. 344 Martian days, or sols,  

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have passed since Spirit’s mission boldly began. 
The whole World was watching as it entered  

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the atmosphere at over 19,500 km/h before 
impacting into Mars’ expansive red desert.  

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During those first sols the lonely rover faced 
mission-threatening software and hardware issues,  

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but it defiantly ventured way past its 90 sol 
life expectancy to share thousands of images of  

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Mars as well as evidence for the existence of 
water on the red planet. In the last episode,  

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we left Spirit climbing to the top of Husband 
Hill wondering what secrets it will uncover  

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below the red planet’s surface and whether it 
will succeed with its grand mission objectives.

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I’m Alex McColgan and you are watching Astrum. 
Join me today to continue with Spirit’s journey  

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as it reaches the summit of Husband Hill and 
pushes on to territory NASA never expected  

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to reach. We will highlight Spirit’s major 
discoveries and follow our trusted rover to  

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the very end. This is a journey as full with 
scientific discovery as it is with adversity,  

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one whose legacy continues to inspire us 
to this day, 20 years after it landed.

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We rejoin Spirit on the week of its first 
anniversary of landing on Mars. To celebrate, it  

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is studying a rock named “Champagne” on the slopes 
of Husband Hill; yes, even robots need to party!  

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And as a robot, it enjoys its ‘Champagne’ in the 
most socially unacceptable way possible: alone and  

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with full use of its science payload. To recap, 
this contains: The Rock Abrasion Tool (RAT), which  

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exposes the fresh surface of a rock of interest, 
the microscopic imager (MI), that is able to  

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capture fine details of a rock’s structure to 
learn about its composition; the alpha particle  

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x-ray photometer (APXS), used to measure the 
elemental makeup of a sample, and the Mössbauer  

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spectrometer (MB) which is used to analyse 
mineralogy, or the chemical makeup, of the rock.

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After these measurements, however, the Spirit 
team confirmed the existence of a minor short  

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circuit of 0.1 V. This short wouldn’t affect 
the day-to-day operations of the rover but it  

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would make Spirit more vulnerable to subsequent 
damage. Otherwise, Spirit was doing well, the team  

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continued to traverse up the soft dusty slopes 
in increasingly complex manoeuvres to ensure  

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that our rover didn’t become trapped - a traverse 
complicated by increased dust in the atmosphere,  

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reducing the sunlight reaching Spirit’s solar 
panels. Some of that dust had settled as a coating  

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layer on the panels, which meant that Spirit’s 
team needed to be extremely careful with how  

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they planned their route and power consumption. 
Nevertheless, en route to Larry’s Lookout, a point  

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on Cumberland Ridge, Spirit analysed two small 
rocks of interest - Peace and Alligator - before  

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imaging a far larger rock much further away, but 
one the rover can never hope to reach: Phobos,  

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Mars’ largest moon, a 26 km wide satellite that is 
due to impact Mars’s surface in 10 million years.

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With its imaging tasks completed, Spirit ventured 
forth across Cumberland Ridge, but only briefly,  

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before it made an unplanned stop! NASA’s engineers 
noticed that Spirit had curiously churned up an  

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intriguing area of soil during its manoeuvres 
named Paso Robles. But what was it about this  

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area of soil that captured NASA’s interest? Paso 
Robles was found to contain incredible levels of  

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salt and high levels of phosphorus. “We're 
still trying to work out what this means,  

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but clearly, with this much salt around, water 
had a hand here.” A stunning and fortuitous  

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find about the history of water on Mars, one 
that preceded another unexpected discovery  

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through failure that we’ll reveal later.
 
To complete its journey to Larry’s Lookout  

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Spirit deftly reversed large sections, this 
manoeuvre helped to relieve pressure on the  

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failing front wheel; instead of moving forward 
and pushing the struggling wheel into the ground,  

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reversing the rover up the slopes dragged the 
wheel across the surface, saving Spirit energy.

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From Larry’s Lookout, Spirit took this panorama on 
sol 413. To the right we can see Spirit’s tracks,  

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to the left is a rocky outcrop which 
is part of the Cumberland ridge,  

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beyond that lies the Tennessee Valley. 
This image was made with 108 frames,  

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each composed of 5 images taken 
through Spirit’s different filters,  

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which creates an approximate true colour image. 
In the centre of the image, 200 m away and 45 m  

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higher in elevation is the summit of Husband 
Hill, Spirit’s next destination. This was to  

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be a difficult and energy consuming journey, 
but Spirit had a chance encounter that greatly  

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improved its prospects. Mars dust devils 
on sol 421 swept over the rover, clearing  

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a years’ worth of dust buildup and increasing 
its solar panel efficiency from 60% to 93%!

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Over the next 160 sols Spirit tackled its way to 
the top. The increase in energy supply meant that  

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Spirit was able to upload its data every sol 
with the Odyssey orbiter, allowing the team to  

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capture lots of information en route including 
on samples Paso Robles 2, Big Clod, Paso Dark,  

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Methuselah, Keystone, Pittsburgh, Independence and 
Franklin without filling up its limited storage.

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On sol 581, Spirit reached the first summit 
of Husband Hill, but our hard-working rover  

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had no intention to stand idle. It took 
a 360º panorama composed of 653 images,  

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for the first time imaging the entire 
deck of the rover in a panorama.  

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Look how clean those panels are! During 
the nights on top of Husband Hill,  

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Spirit also imaged both moons, Phobos and Deimos 
in order to measure their orbits more accurately.

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In the panoramic image McCool Hill and Ramon 
Hill are off into the distance in the centre.  

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McCool Hill was to be its winter destination, 
an area where Spirit could park up and angle its  

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panels to the sun to maximise its energy capture 
over the darker months. But it never reached it.

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So let’s continue with Spirit’s journey to see 
what it can achieve in its final 2.6 kms of life.

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On the descent of Husband Hill, Spirit 
was able to collaborate with the Hubble  

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telescope to help calibrate data with 
atmospheric opacity readings, a sky survey  

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and calibration target readings. These helped 
with the accuracy of Spirit’s measurements.

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Incredibly, Spirit’s capability increased 
several times in its life, despite being  

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142 million kilometres away from its team of 
engineers. The multitasking rover installed an  

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update as it was climbing Husband Hill, giving 
it the ability to drive sections autonomously,  

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and another on sol 1067 allowed Spirit to 
decide if and when to upload images and  

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whether to extend its arms to examine rocks. 
Spirit gained independence as it matured.

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There was one decision that the NASA 
controllers still took on the descent of  

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Husband Hill, though: which rock to analyse out 
of a choice between two: “Comanche” and “Miami”.

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Commanche was chosen, and it turned out to 
be a rich subject to analyse. On sol 690,  

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Spirit discovered that Comanche 
was 1/4 magnesium iron carbonates,  

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around 10 times higher than any rock previously 
analysed on Mars. Carbonates are important in  

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further understanding the hydrological history of 
Mars as they are formed in the presence of water,  

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but dissolved by acid. So their discovery in high 
levels suggested that more neutral and hospitable  

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bodies of water existed that could have been home 
to primitive life much earlier in Mars’ history.

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A great discovery, but Spirit continued on 
tirelessly and it reached its next checkpoint  

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on sol 744 (Visuals showing Home Plate). Home 
Plate features layered and weathered rocks,  

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including this feature found on the 
outskirts. It’s hard to imagine this  

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being shaped by anything other than flowing water!

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But it was the flow of time that was shaping 
Spirit. The rover was charging towards the  

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north facing slopes of McCool Hill in March 2006 
when one of its wheels failed. Exhaustive tests  

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back on Earth at the JPL test facility replicating 
the failure could not get the wheel moving again,  

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Spirit was now only making progress by 
dragging the locked right-front wheel.  

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Martian winter was coming, too, and as the 
light fades so too do Spirit’s reserves. With  

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these two factors combined, NASA made the 
call to abort the drive to McCool hill in  

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favour of Low Ridge Haven. The rover 
found a spot with an incline of 11º,  

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which was sufficient to see Spirit 
make it through another Martian winter.

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For around 8 months, Spirit remained on the 
ridge taking images of its surroundings. In  

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one of the images, engineers spotted 
two subjects that were possible iron  

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meteors. These were given the names: Zhong 
Shan after the Chinese Antarctic base,  

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and Allan Hills after an area in Antarctica 
where several Martian meteorites have been  

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discovered. Including the most well known and 
noteworthy of these, ALH84001.Found in 1996,  

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NASA scientists suggested that this Martian 
meteorite may contain fossilised extraterrestrial  

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life and released this image you may recognise 
as it became front page news the world over.

00:10:44.160 --> 00:10:50.080
Once the Martian winter was over, Spirit had 
far more energy to use and it ventured out once  

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again. In March 2007, Spirit unwittingly 
excavated a surprising discovery. In the  

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soft and red Martian soil, Spirit’s failed 
wheel gouged the Martian surface exposing  

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bright white silica. Not evidence for life, 
per se, but the next best thing. Evidence  

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for the potential of life. In our video on the 
origin of life we talked about deep sea vents  

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and areas where hot gases and material 
from below the crust meets the Earth’s  

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surface. Some create the potential for life to 
start, others offer life a haven for growth.  

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NASA believed that the silica deposit 
was made in one of two environments: 

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hot spring deposits, where hot water dissolves 
silica in one place and then deposits it  

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elsewhere, like hot springs or geysers. or 
ii) acidified steam blasting existing rocks  

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stripping them of much of their minerals leaving 
mostly silica behind, areas known as fumaroles.

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Whichever it was, both environments 
are very supportive of microbial life  

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on Earth! Incredible to think, 
if Spirit had not malfunctioned,  

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if it and NASA had given up too early, 
this discovery would never have been made.

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Spirit spent the next few months 
circling Home Plate and in June  

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2007 received another life-saving 
spring clean of its solar panels.  

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Spirit boosted its power generation 
from a dip of 120 w/h back to over 600!  

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On November 6th, Spirit navigated to the western 
side of Home Plate and took another panorama. NASA  

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published this photo as a “Astronomy Picture of 
the Day”, which on first inspection looked like  

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every other photo taken of the Martian landscape. 
But it was soon to receive worldwide attention!  

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Can you spot it? Hiding in plain sight is a 
suspected humanoid life-form. Let’s zoom in to  

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what was dubbed ‘Little Bigfoot’. On the right 
of the image we can also see Spirit’s tracks  

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from Husband Hill! We are now a few hundred 
metres away from the end of Spirit’s journey.

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Martian storms had been increasing 
in recent months, leaving the solar  

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panels heavily covered with dust as well as 
blocking up to 99% of the light through the  

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atmosphere. Survival was becoming harder and 
operations were now much reduced from its peak.  

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The ageing Spirit was generating only 128 w/h 
which is less than the 150 w/h it requires to  

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keep itself warm If the heating fails then the 
rover’s components will eventually fail, too.

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Two small cleaning events took the energy 
output of the solar arrays to 372 w/h. This  

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gave the rover enough energy to charge 
its batteries and begin to move again.  

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But the flow of time is always cruel. Spirit 
began to experience unexplained memory gaps  

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in April 2009 with the rover now only 
4 metres away from its resting place.

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On sol 1892 Spirit hit incredibly soft 
dusty soil at a location named Troy,  

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where Spirit would make its last stand. 
Underneath its wheels was jarosite,  

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which is a mineral of iron(iii) sulphate. 
Jarosite has remarkably low cohesion meaning  

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that achieving enough traction to move was 
proving impossible. Despite efforts by the  

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JPL back on Earth to explore techniques to escape 
the sand trap no progress was made. On sol 2155,  

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NASA reclassified the mission as a stationary 
research platform. While there our rover took  

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measurements of the atmosphere and several more 
images, including its last panorama from Troy.

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Spirit was still able to perform soil studies 
and extraction tests because the functionality  

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of its arm was still excellent. Spirit needed to 
have a busy research schedule to use the power it  

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was generating to maintain good battery health. 
But the final winter was approaching for Spirit,  

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and it was a bitter one. Over the next few 
months, the power generation continually dropped,  

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and by sol 2196 it was again down to the 
critical 150 w/h. Sometime on sol 2208,  

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it is believed Spirit suffered a low-power fault.

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On a lifeless and quiet planet, Spirit’s end was 
never going to be dramatic, but that’s not to  

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say Spirit went gently into that good night. Now 
forgotten by many who watched Spirit’s landing,  

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it came to rest on the edge of Home 
Plate, alone, with two broken wheels,  

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a drained battery and a legacy 
of scientific discovery.

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In its life of 2088 sols, Spirit journeyed 7.7 
kilometres and transferred over 128,000 images  

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back to Earth. Its mission was an overwhelming 
success, achieving its objectives to further  

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the understanding of the history of water – 
and the chance for life – on Mars. Its name  

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lives on in the name of asteroid 27452 
Spirit, and the Perseverance rover is  

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carrying its memory today; with this, 
a family portrait of the Mars vehicles.

00:16:41.600 --> 00:16:47.120
Spirit’s story is one of overcoming. 
Both the Spirit and Opportunity rovers  

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lived up to their names given to them 
by a seven year old girl called Sofi;  

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names inspired by the struggles and promise 
of her own childhood. So it’s fitting that as  

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the Spirit’s internal heaters turned off, 
as it froze under the Martian star-scape,  

00:17:03.680 --> 00:17:09.760
the rover’s story came full circle and found 
its end right where it began with Sofi’s:

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“It was dark and cold and lonely. At night,  

00:17:13.200 --> 00:17:23.400
I looked up at the sparkly sky and felt 
better. I dreamed I could fly there.”

00:17:23.400 --> 00:17:29.080
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