Computer generated image of Mars with Gale Crater catching the morning light, image credit Nasa
Take a look at this computer generated image, that’s Mars, the red planet, the rusty world, and Earth’s neighbour in the solar system. But look closely, and see the crater bathed in the morning sunshine with the unusual looking mound inside it, well that’s the Nasa Mars Curiosity Rover‘s target, Gale Crater. This is in reality much more than a mound if you were stood at the bottom of it looking up. The mound is actually a 3 mile high (5 kilometre) mountain rising from the floor of the 96 miles (154.5 kilometre) wide crater.
The Mountain
So at first this had me scratching my head, “Just how come there’s a dirty great mountain slap bang in the middle of an impact crater?” Any asteroid/comet worth its salt is going to dig out a pretty decent sized bowl shape crater in a planet’s surface, no messing. Well yes this is what originally happened here around 3.5 billion years ago when Mars (and Earth) was taking a cosmic beating from anything and everything large and rocky floating out there in space.
But scientists now suspect that over many millions of years sediments flowed into Gale when Mars was wetter and warmer than it is now. Over time layer upon layer was deposited, eventually filling in the original bowl shape left by the space object. Over further eons, the actions of wind and water went to work and carved out the spectacular mountain in the centre, nicknamed Mount Sharp, revealing layers and layers of rock. From the oldest rock way back in Mars’ history at the base of the mountain, to the very youngest depicting more recent times further up near the top. It’s all laid out, a Martian timeline for Curiosity to read like a book of the red world’s geological past.
Gale Crater showing Curiosity’s landing target
Location, Location, Location
So we have the layered mountain, that’s great, but there’s more to it than that. This particular spot on the Martian landscape was also picked for just where it is, and it has everything to do with H2O, water, the cool wet stuff we all know and love. We both know that where there’s water there’s usually life, it’s the best solvent for it, that’s true on planet Earth anyway. So Curiosity is looking for environments that might have been cosy enough for any simple alien critters to exist on Mars, way back when. As it happens, Gale Crater lies right near the boundary between two distinct regions of Mars, called the hemispheric dichotomy, this is also near the Martian equator. The southern region of Mars is a high and rugged landscape, while the northern area is lower and smoother. The southern area actually has a thicker crust that the north, on average a hefty 26 kilometres thicker. This strange feature is thought to have been caused by a catastrophic collision billions of years ago.
The southern highlands (orange) & northern lowlands (blue)
But there’s one thing Mars can’t quite manage to keep a mystery, and that is water flows from high areas to low areas, just like everywhere else in the universe. Scientists think that the lower location of Gale Crater is perfect because it could have had large amounts of water flowing into it from the neighbouring higher southern regions for large periods of time. Considering the size of Gale Crater, the water would have had plenty of space to pool into lakes in the times when Mars’ was a warmer, and potentially more life friendly place.
The Rover
This robotic rover is nuclear powered not solar powered like the previous rovers Spirit and Opportunity, so no problems with dust covering any solar panels on Curiosity. The Mars Science Laboratory which is its official name, packs a punch in size and weight. Being as large as a compact car and over 5 times heavier than robotic geologists Spirit or opportunity, MSL’s onboard science arsenal tips the scales at 15 times the weight of the previous rovers. Curiosity is not able to actually detect Martian life, but is able to chemically analyse rocks and soil for the ingredients that could, or could have supported microbial life. Curiosity takes rovers that have gone before it one step further, now we’ll have a robot geochemist roaming the red planet.
Who knows what new Martian science awaits us.
John Brady