The Curiosity Rover's 9 Biggest Moments from Three Years on Mars
Mars Radiation levels are comparable to those on the ISS
Curiosity was the first rover to measure radiation levels on another planet, and the results were surprising. It found that the radiation levels on the Red Planet were similar to those experienced by astronauts on the ISS, which would make a potential manned round trip to Mars feasible. Colonization is another story entirely, but the results were still encouraging.
Curiosity drills into a Martian rock
In February 2013, Curiosity became the first rover to drill into an extraterrestrial rock. It bore 2.5 inches into a Mars outcrop dubbed "John Klein," revealing the several groundbreaking insights into the early chemical composition of the Red Planet.
Curiosity took the selfie craze to Mars by taking several photos of itself, using the Mars Hand Lens Imager instrument:
"Self portraits... document the state of the rover and allow mission engineers to track changes over time, such as dust accumulation and wheel wear," said NASA.
Mars was once host to liquid water
Only seven weeks after its historic landing, Curiosity found an ancient streambed that was once host to liquid water. The water flowed approximately knee-deep in this small stream, which may very well mean that the surrounding area was once habitable, as life tends to originate around bodies of water on Earth.
But possibly even more momentous was a more recent discovery: that the infamous Gale Crater not only housed a Martian lake, but underwent cycles of wet and dry periods over tens of millions of years. This sustained filling and drying of the lake made it more likely that microbial life had a chance to emerge.
Key elements for life
In the John Klein rock, Curiosity discovered key elements for life in the chemical composition of Mars from billions of years ago, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon, as well as clay minerals that indicated a former body of water that was neutral in pH.
Then, earlier this year, Curiosity found solid nitrogen that is currently extant on Mars, paving the way for discovering extraterrestrial organisms.
There may currently be liquid water on Mars
Curiosity found the first evidence that water exists on Mars today, in the form of a type of salt called perchlorates, which lower the freezing point of liquid water by up to 70 degrees. As Mars was thought to be too cold to house liquid water in its current environment, this was a major discovery.
Microbial life once existed on Mars
In January, Curiosity took photos of Mars's surface that depicted not only dry lakebeds, but sedimentary structures that are similar to those built by microbes on Earth. Scientists believe that this is evidence of the emergence of microbial species on Mars that are now extinct.
First signs of life on Mars
Curiosity discovered the first-ever evidence that there may be life on Mars when it detected spikes of methane gas, which is a key indicator of bacterial presence.
Soon afterwards, Curiosity found fatty acids on Mars. As fatty acids are one of the building blocks of organic molecules, this provided further evidence that there may be some kind of organism currently living on Mars.
Curiosity discovers Martians
Pareidolia, the effect that allows for constellations, funny cloud shapes, and Rorschach tests, is defined as "a psychological phenomenon involving a stimulus (an image or a sound) wherein the mind perceives a familiar pattern where none actually exists." Most entertainingly of all, this phenomenon has led to the discovery of many a Martian in Curiosity photos, including the "Mars rat":
A baby Martian skeleton:
And don't forget this photo of a "little green man" lying on a rock:
And in case you have trouble seeing it, here's an "enhanced" photo:
These results are all very recent, with neither the methane gas nor the fatty acids fully confirmed, but detecting the first possible signs of alien life (and real aliens!) is an enormous accomplishment, especially for only three years. Happy anniversary, Curiosity!