Five Pictures from Ten (Earth) Years of Curiosity

 

The photos that our robot geologists (and robot atmospheric scientists) bring back to us from other worlds help us to relate to these places on a human scale. No one at the PVL have looked at more images of Mars than Alex and so, who better to take us on a visual trip down memory lane on this auspicious anniversary?

By Alex Innanen

August 6^th marks 10 (earth) years since Curiosity (AKA the Mars Science Laboratory or MSL, because space people love a good acronym) landed in Gale Crater on Mars. If you’ve been around the blog, you’ll know that many PVL-ers have had the chance to work on the mission (myself included) and there have been a plethora of posts over the years about what doing ENV operations is like, or what cool science MSL is doing, or other big mission events, like the 2018 global dust storm or passing 2000 sols on Mars. To add to this collection, and to celebrate 10 years of Curiosity (or 5 Mars years, a milestone reached this most recent January), I’m going to journey through some of my favourite pictures the rover has taken over the past decade.

First we have the above picture, a classic selfie. Curiosity regularly poses for MAHLI (the Mars Hand Lens Imager) to take these self portraits, which are actually mosaics of tens of MAHLI images. There’s a fantastic video of Curiosity’s arm moving around to get all the pictures that make up a selfie. This particular selfie was captured during the 2018 global dust storm, and you can see dust in the background obscuring the crater rim. This is the same dust storm that heralded the end of Opportunity’s mission, but Curiosity came through with lots of science (and nifty pictures) to show for it.

Going all the way back in time to 2012, this is a 360° panorama of Curiosity’s landing site, named ‘Bradbury’ for the sci-fi author Ray Bradbury. Right in the centre of the picture is Mount Sharp (or Aeolis Mons), the mountain in the centre of Gale Crater. Mount Sharp is made up of sediments laid down in Gale Crater over a long period of Mars’ history, and as Curiosity has climbed up it, it’s as though the rover has been travelling through that history. But first it had to get to the base of Mount Sharp, a trip which took around 2 years trundling through the remnants of ancient lakes and rivers. I love looking at this panorama because it gives a great idea of how far Curiosity has traveled – over 28 km and 600 m of elevation, now. It's also a great ‘big picture’ shot – every new location Curiosity visits is (in my humble opinion) stunning and unique in its own way, with so much new and exciting to look at. This image lets you take a step back and take it all in.

It would be remiss of me to not include a cloud picture, so here it is, my absolute favourite cloud shot. I may be slightly biased, as I was on shift when this image was planned, but it’s so dramatic, with the cliff face (called ‘Mont Mercou’) in the foreground and the glowing clouds behind. These are Noctilucent clouds, which means ‘night shining’, and were captured at twilight early this Mars year (which was actually March of 2021 – Mars years are long). These kinds of clouds are high up in the atmosphere, and are illuminated by the setting sun, even visible when the sun has gone below the horizon. This is what makes them appear to glow, still being illuminated while the rest of the sky darkens. These particular twilight clouds seem to form more readily in Gale crater near the beginning of the Mars year, something the team discovered in Mars year 35. At the start of Mars year 36 (the current Mars year) we started looking for them and were not disappointed. One of the great things about Curiosity having been on Mars for so long is the fact that we can see yearly repetitions like this and come up with a better idea of what the Martian environment is up to year after year.

Mars’ blue sunset is spectacular and well known to fans of the ‘red’ planet. But “what colour is the Martian sky?” is a question I’ve been asked more than once by those less familiar with Mars. And it’s a great question! Sometimes – like in this picture or the cloud picture above, the sky looks more blue, almost like earth’s sky. But at other times, like in the selfie or the Mount Sharp panorama, it looks more orange or yellow. There’s a few factors behind this – often images are colour-corrected (‘white-balanced’) to show what a scene might look like under earth-like lighting. This can help scientists interpret features within a scene, making them look more familiar to better compare to earth, but doesn’t accurately represent what you might see if you were standing on the surface of Mars, which would be more of a yellowy-orange sky.

Except when you get close to the sun, like in this sunset picture. Much like how earth’s scatters light, giving us a blue sky, so too does dust in the Martian atmosphere, but the blue wavelengths of light mostly scatter forwards, so the blue colour appears closer to the sun. As the sun sets, there is more atmosphere and more dust for the light to scatter through, so that blue effect near the sun becomes more pronounced. 

I’m going to finish with this absolute stunner of an image, which combines two NavCam (Navigation camera) mosaics of the same scene, one taken in the morning and one in the afternoon. They were combined to show different landscape features that are highlighted as the sun illuminates some regions and casts others into shadow. After talking about the colours of Mars, you may be wondering what gives this image its striking blue and yellow palette. The NavCams on Curiosity only take pictures in black and white – colour was added to this image after the fact to highlight the lighting changes, with blue showing morning features, yellow showing evening features, and their combination showing just that – a combination of the two. This picture is looking back down Mount Sharp towards the crater rim in the distance, and it seems like a fitting image to close this blogpost on, looking back over the last great 10 years with Curiosity.