(CNN) -- One of the first photos it sent home showed a self-portrait of its shadow. The dark gray specter of machinery against a lighter grainy backdrop showed up minutes after the news of its arrival, as if to say "I'm here!"
With its cameras as our eyes, it opened our minds to un-roved territory. If you're a NASA engineer, you might even call it "she."
Curiosity, NASA's most sophisticated and complex Mars rover, touched down on the Red Planet on the morning of August 6, 2012 (August 5 if you're in Pacific Daylight Time). The $2.5 billion mission set out to explore Gale Crater, which was thought to have once hosted flowing water, and find out if that environment was once habitable.
Spoiler alert: It was.
But that's not all the rover found while traveling 1.6 kilometers across Mars' barren surface during its 12 months on the planet. Curiosity has collected 190 gigabits of data and sent back more than 36,700 full images and 35,000 thumbnail images, NASA said. The rover has also fired more than 75,000 laser shots to help scientists analyze the composition of material, and collected samples from two rocks.
The Curiosity rover took this image on September 10 of a rock formation informally dubbed "Darwin," first noted from the orbiting spacecraft. Scientists had the rover stop in this region, called Waypoint 1, because it appears to be a prime area to study the inner makeup and history of the floor of the Gale Crater. Analysis of Darwin may provide evidence of whether and how water played a role in the layering of rocks in this region. The rover touched down on Mars on the morning of August 6, 2012, with a mission to explore Gale Crater, which was thought to have once hosted flowing water, and find out if that environment was once habitable.
Photos: Mars rover Curiosity
NASA scientists joke that the "warranty" on Curiosity is two years, since that was the rover's design specification, said Ashwin Vasavada, deputy project scientist for the Mars Science Laboratory Mission. But other robotic vehicles have far outlasted their projected lifetimes. NASA landed twin rovers Spirit and Opportunity on Mars in 2004, and Opportunity is still chugging along. (Spirit stopped communicating in 2010).
Now, Curiosity is on its way to Mount Sharp, a three-mile-high structure made of layers that, scientists believe, recorded Mars' geological history.
"It's a lot of work and a lot of people involved, but it's wonderful in the sense that it's really capable scientifically," Vasavada said of the rover. "We're always amazed at how much we can do through this robot."
To mark the anniversary of its first year on Mars, Curiosity played "Happy Birthday" to itself Monday night, using an on-board instrument to beep out the tune. No word on whether anyone was listening.
Here are five fascinating milestones from Curiosity's first 12 months:
1. OMG, it actually landed. #mindblown. How do you land a two-ton, car-sized rover on another planet? Engineers thought about it a lot, and came up with a complex plan requiring a sky crane and the world's largest supersonic parachute. The acrobatic maneuvers required to get it safely to the ground were dubbed the "seven minutes of terror," as featured in a NASA video simulation depicting just how many things had to go right to get the rover on the ground in one piece.
Adam Steltzner, lead engineer overseeing the rover's arrival, told reporters a few days before the big night, "I promise you it is the least crazy of the methods you could use to get a rover the size of Curiosity on Mars."
For the social media generation, this was our moon landing.
The Internet went wild over a rover flight director who showed up for work on landing night with a mohawk, got hailed as "Mohawk Guy," and later received a shout-out from President Barack Obama. Curiosity itself has a verified Twitter account (with 1.3 million followers), and tweeted that night, "I'm safely on the surface of Mars. GALE CRATER I AM IN YOU!!! #MSL."
"The overall highlight, I think, even a year later, still is planning successfully and seeing Gale Crater for the first time," Vasavada said. He added: "We landed much more smoothly than we ever rehearsed it."
2. Life on Mars could have existed. This was the major science highlight of Curiosity's inaugural Martian year, Vasavada said. Although this discovery builds upon previous ideas, Curiosity provided enough confirmation for scientists to finally come out and say it: The environment Curiosity has been exploring was once habitable.
"We now know Mars offered favorable conditions for microbial life billions of years ago," said the mission's project scientist, John Grotzinger of the California Institute of Technology.
Curiosity became the first robot to drill on another planet, and the powder on the drill bit gave the scientists sufficient evidence to say that life could have survived in that area. The drill material had chemicals important for life in it, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon. Also excitingly for scientists, the sample contained a type of clay that forms in the presence of water.
The rover's Mast Camera (Mastcam) additionally spotted evidence of water-bearing minerals in the Yellowknife Bay area where Curiosity first drilled. Scientists detected minerals using the camera's infrared-imaging capability.
Gallery: Curiosity's best photos of the Red Planet
This area that Curiosity has been exploring is part of an alluvial fan, a formation of debris left by a river that once flowed into the crater, scientists say.
"We investigated the fan and found evidence that there was very likely an intermittent lake that had freshwater at one point," Vasavada said.
3. Mars is red on top, gray below. That material in the drill bit that the rover used to probe rock wasn't the same orange color that's so familiar to us from the rover's photography. Instead, it was gray, scientists said in February.
"You can probably bet that when things turn orange, it's because there's a rusting process of some kind going on that oxidizes the iron in the rock," Joel Hurowitz, sampling system scientist for Curiosity at NASA's Jet Propulsion Laboratory, said at the time.
4. The planet's atmosphere was destroyed a long time ago. Using instruments on board Curiosity, scientists determined that the Martian atmosphere hasn't changed much in the last 4 billion years, and during that whole time it has been thin, as well as inhospitable to life as we know it.
Initially, however, after the planet formed 4.5 billion years ago, the planet's atmosphere was 100 times denser than the Earth's atmosphere, scientists say. Their results were published in the journal Science in July.
We could learn even more about the atmosphere from NASA's Mars Atmosphere and Volatile Evolution Mission orbiter, which is expected to launch in November. This spacecraft will have techniques to measure the current rate of loss of the atmosphere.
5. Radiation makes the trip to Mars dangerous for humans. Curiosity spent 253 days getting to Mars in 2012. During that time, the mission (officially called Mars Science Laboratory) was collecting data about radiation on the journey to the Red Planet using the Radiation Assessment Detector device.
An analysis of this data, published in the journal Science in May, found that Mars-bound pioneers would be exposed to radiation levels that could effectively retire astronauts under NASA's current standards.
"The radiation environment in deep space is several hundred times what it is on Earth, and that's even inside a shielded spacecraft," said Cary Zeitlin, principal scientist for the Martian Radiation Environment Experiment. Scientists are working on faster engines to shorten the trip to Mars, and may be able to conceive of a spacecraft with better shielding.
501 days in space with your spouse: Could you handle it?
What's next? Drive, drive, drive!
The rover's second year will be mostly about the five-mile drive to Mount Sharp, Vasavada said.
So far, Curiosity has stopped a lot to test out its instruments, collecting and analyzing samples and exploring particular areas. Now, it will drive as far as it can every day -- but not at Earthly highway speeds. Vasavada's hope is to get the rover to Mount Sharp by next summer.
During the drive, the rover will continue snapping photos, and the meteorological instruments will still take measurements. Curiosity will stop if it spots anything -- a structure or formation, or the improbable Martian -- that looks interesting to scientists.
In 2020, another NASA rover is planned to join the small fleet of human-made vehicles on Mars. This one may be able to collect samples for potential return to Earth, and test technology relevant to human exploration.
Meanwhile, the Opportunity rover rolls along, in its 10th year, exploring Mars on the opposite side of the planet from Curiosity.
None of these rovers may ever meet. But perhaps their tracks will mark the paths where humans will someday tread.
Buzz Aldrin: Get to Mars within 20 years
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The 2,000-pound rover Curiosity landed on Mars on August 6, 2012, and has been sending back fascinating images and data ever since. Curiosity recently began a trek toward Mount Sharp after spending more than six months in the "Glenelg" area. This image was taken on July 16, after the rover passed the 1 kilometer mark for the total distance covered since the start of the mission. It still has over 8 kilometers (5 miles) to cover before reaching Mount Sharp, which will take several months.
The lower slopes of Mount Sharp are visible at the top of this image, taken on Tuesday, July 9. The turret of tools at the end of the rover's arm, including the rock sampling drill in the lower left corner, can also be seen.
This image taken by the rover on Monday, July 8, shows the tracks left behind after its first drive away from the "Glenelg" area, covering roughly 60 feet.
Curiosity drilled into the rock target, called "Cumberland," on May 19, and collected a powdered sample of material from the rock's interior. The sample will be compared to an earlier drilling at the "John Klein" site, which has a similar appearance and is about nine feet away.
Mars once had conditions favorable for microbial life, NASA scientists announced Tuesday, March 12, 2013. One piece of evidence for that conclusion comes from this area of the Martian surface, nicknamed "Sheepbed." It shows veins of sediments that scientist believe were deposited under water and was an environment once hospitable to life.
The rock on the left, called Wopmay, was discovered by the rover Opportunity, which arrived in 2004 on a different part of Mars. Iron-bearing sulfates indicate that this rock was once in acidic waters. On the right are rocks from Yellowknife Bay, where rover Curiosity is situated. These newly discovered rocks are suggestive of water with a neutral pH, which is hospitable to life formation.
NASA's Curiosity rover shows the first sample of powdered rock extracted by the rover's drill. In subsequent steps, the sample will be sieved to be analyzed. The image was taken by Curiosity's mast camera on Wednesday, February 20.
The rover drilled this hole, in a rock that's part of a flat outcrop researchers named "John Klein," during its first sample drilling on Mars on February 8.
The latest self-portrait of the rover combines dozens of images taken by the rover's Mars Hand Lens Imager (MAHLI) on February 3.
NASA's Mars rover Curiosity has taken its first set of nighttime photos, including this image of Martian rock illuminated by ultraviolet lights. Curiosity used the camera on its robotic arm, the Mars Hand Lens Imager, to capture the images on January 22.
Another nighttime image includes this rock called Sayunei in the Yellowknife Bay area of Mars' Gale Crater. Curiosity's front-left wheel had scraped the rock to inspect for fresh, dust-free materials in an area where drilling for rock soon will begin.
Other night photos includes this image of the calibration target for the Mars Hand Lens Imager camera at the end of the rover's robotic arm. For scale, a penny on the calibration target is three-fourths of an inch in diameter.
A view of what NASA describes as "veined, flat-lying rock" selected as the first drilling site for the Mars rover taken on January 10.
Curiosity used a dust-removal tool for the first time to clean this patch of rock on the Martian surface on January 6.
The rover captured this mosaic of images of winding rocks known as the Snake River on December 20, 2012.
A view of the shallow depression known as "Yellowknife Bay," taken by the rover on December 12, 2012.
The Mars rover Curiosity recorded this view from its left navigation camera after an 83-foot eastward drive on November 18, 2012. The view is toward "Yellowknife Bay" in the "Glenelg" area of Gale Crater.
Three "bite marks" made by the rover's scoop can be seen in the soil on Mars surface on October 15, 2012.
The robotic arm on NASA's Mars rover Curiosity delivered a sample of Martian soil to the rover's observation tray for the first time on October 16, 2012.
This image shows part of the small pit or bite created when NASA's Mars rover Curiosity collected its second scoop of Martian soil on October 15, 2012. The rover team determined that the bright particle near the center of the image was native to Mars, and not debris from the rover's landing.
This image shows what the rover team has determined to be a piece of debris from the spacecraft, possibly shed during the landing.
The rover's scoop contains larger soil particles that were too big to filter through a sample-processing sieve. After a full-scoop sample had been vibrated over the sieve, this portion was returned to the scoop for inspection by the rover's mast camera.
This 360-degree panorama shows the area where the rover will spend about three weeks collecting scoopfuls of soil for examination. The photo comprises images taken from the rover's navigation camera on October 5, 2012.
An area of windblown sand and dust downhill from a cluster of dark rocks has been selected as the likely location for the first use of the scoop on the arm of NASA's Mars rover Curiosity.
Curiosity cut a wheel scuff mark into a wind-formed ripple at the "Rocknest" site on October 3, 2012. This gave researchers a better opportunity to examine the particle-size distribution of the material forming the ripple.
NASA's Curiosity rover found evidence for what scientists believe was an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here. The key evidence for the ancient stream comes from the size and rounded shape of the gravel in and around the bedrock, according to the Jet Propulsion Laboratory/Caltech science team. The rounded shape leads the science team to conclude they were transported by a vigorous flow of water. The grains are too large to have been moved by wind.
This photos shows an up-close look at an outcrop that also shows evidence of flowing water, according to the JPL/Caltech science team. The outcrop's characteristics are consistent with rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. Water transport is the only process capable of producing the rounded shape of conglomerate rock of this size.
Curiosity completed its longest drive to date on September 26, 2012. The rover moved about 160 feet east toward the area known as "Glenelg." As of that day the rover had moved about a quarter-mile from its landing site.
This image shows the robotic arm of NASA's Mars rover Curiosity with the first rock touched by an instrument on the arm. The photo was taken by the rover's right navigation camera.
This image combines photographs taken by the rover's Mars Hand Lens Imager at three distances from the first Martian rock that NASA's Curiosity rover touched with its arm. The images reveal that the target rock has a relatively smooth, gray surface with some glinty facets reflecting sunlight and reddish dust collecting in recesses in the rock.
This rock will be the first target for Curiosity's contact instruments. Located on a turret at the end of the rover's arm, the contact instruments include the Alpha Particle X-Ray Spectrometer for reading a target's elemental composition and the Mars Hand Lens Imager for close-up imaging.
Researchers used the Curiosity rover's mast camera to take a photo of the Alpha Particle X-Ray Spectrometer. The image was used to see if it had been caked in dust during the landing.
Researchers also used the mast camera to examine the Mars Hand Lens Imager (MAHLI) on the rover to inspect its dust cover and check that its LED lights were functional. In this image, taken on September 7, 2012, the MAHLI is in the center of the screen with its LED on. The main purpose of Curiosity's MAHLI camera is to acquire close-up, high-resolution views of rocks and soil from the Martian surface.
This is the open inlet where powdered rock and soil samples will be funneled down for analysis. The image is made up of eight photos taken on September 11, 2012, by MAHLI and is used to check that the instrument is operating correctly.
This is the calibration target for the MAHLI. This image, taken on September 9, 2012, shows that the surface of the calibration target is covered with a layor of dust as a result of the landing. The calibration target includes color references, a metric bar graphic, a penny for scale comparison, and a stair-step pattern for depth calibration.
This view of the three left wheels of NASA's Mars rover Curiosity combines two images that were taken by the rover's Mars Hand Lens Imager on September 9, 2012, the 34th day of Curiosity's work on Mars. In the distance is the lower slope of Mount Sharp.
This view of the lower front and underbelly areas of NASA's Mars rover Curiosity was taken by the rover's Mars Hand Lens Imager. Also visible are the hazard avoidance cameras on the front of the rover.
The penny in this image is part of a camera calibration target on NASA's Mars rover Curiosity. The image was taken by the Mars Hand Lens Imager camera.
The reclosable dust cover on Curiosity's Mars Hand Lens Imager was opened for the first time on September 8, 2012, enabling MAHLI to take this image.
The Curiosity rover used a camera located on its arm to obtain this self-portrait on September 7, 2012. The image of the top of Curiosity's Remote Sensing Mast, showing the Mastcam and Chemcam cameras, was taken by the Mars Hand Lens Imager. The angle of the frame reflects the position of the MAHLI camera on the arm when the image was taken.
The left eye of the Mast Camera on NASA's Mars rover Curiosity took this image of the rover's arm on Wednesday, September 5, 2012.
Sub-image one of three shows the rover and its tracks after a few short drives. Tracking the tracks will provide information on how the surface changes as dust is deposited and eroded.
Sub-image two shows the parachute and backshell, now in color. The outer band of the parachute has a reddish color.
Sub-image three shows the descent stage crash site, now in color, and several distant spots (blue in enhanced color) downrange that are probably the result of distant secondary impacts that disturbed the surface dust.
An image released August 27, 2012. was taken with Curiosity rover's 100-millimeter mast camera, NASA says. The image shows Mount Sharp on the Martian surface. NASA says the rover will go to this area.
The Mars rover Curiosity moved about 15 feet forward and then reversed about 8 feet during its first test drive on August 22, 2012. The rover's tracks can be seen in the right portion of this panorama taken by the rover's navigation camera.
NASA tested the steering on its Mars rover Curiosity on August 21. Drivers wiggled the wheels in place at the landing site on Mars.
Curiosity moved its robot arm on August 20, for the first time since it landed on Mars. "It worked just as we planned," said JPL engineer Louise Jandura in a NASA press release. This picture shows the 7-foot-long arm holding a camera, a drill, a spectrometer, a scoop and other tools. The arm will undergo weeks of tests before it starts digging.
With the addition of four high-resolution Navigation Camera, or Navcam, images, taken on August 18, Curiosity's 360-degree landing-site panorama now includes the highest point on Mount Sharp visible from the rover. Mount Sharp's peak is obscured from the rover's landing site by this highest visible point.
This composite image, with magnified insets, depicts the first laser test by the Chemistry and Camera, or ChemCam, instrument aboard NASA's Curiosity Mars rover. The composite incorporates a Navigation Camera image taken prior to the test, with insets taken by the camera in ChemCam. The circular insert highlights the rock before the laser test. The square inset is further magnified and processed to show the difference between images taken before and after the laser interrogation of the rock.
An updated self-portrait of the Mars rover Curiosity, showing more of the rover's deck. This image is a mosiac compiled from images taken from the navigation camera. The wall of Gale Crater, the rover's landing site, can be seen at the top of the image.
This image shows what will be the rover's first target with it's chemistry and camera (ChemCam) instrument. The ChemCam will fire a laser at the rock, indicated by the black circle. The laser will cause the rock to emit plasma, a glowing, ionized gas. The rover will then analyze the plasma to determine the chemical composition of the rock.
This is a close-up of the rock that will be the ChemCam's first target.
This image, cropped from a larger panorama, shows an area, near the rover's rear left wheel, where the surface material was blown away by the descent-stage rockets.
This image, with a portion of the rover in the corner, shows the wall of Gale Crater running across the horizon at the top of the image.
This image, taken from the rover's mast camera, looks south of the landing site toward Mount Sharp.
This partial mosaic from the Curiosity rover shows Mars' environment around the rover's landing site on Gale Crater. NASA says the pictured landscape resembles portions of the U.S. Southwest. The high-resolution mosaic includes 130 images, but not all the images have been returned by the rover to Earth. The blackened areas of the mosaic are the parts that haven't been transmitted yet. See more on this panaroma on NASA's site.
In this portion of the larger mosaic from the previous frame, the crater wall can be seen north of the landing site, or behind the rover. NASA says water erosion is believed to have created a network of valleys, which enter Gale Crater from the outside here.
In this portion of the larger mosaic from the previous frame, the crater wall can be seen north of the landing site, or behind the rover. NASA says water erosion is believed to have created a network of valleys, which enter Gale Crater from the outside here.
Two blast marks from the descent stage's rockets can be seen in the center of this image. Also seen is Curiosity's left side. This picture is a mosaic of images taken by the rover's navigation cameras.
A color image from NASA's Curiosity rover shows the pebble-covered surface of Mars. This panorama mosaic was made of 130 images of 144 by 144 pixels each. Selected full frames from this panorama, which are 1,200 by 1,200 pixels each, are expected to be transmitted to Earth later.
A panoramic photograph shows the Curiosity rover's surroundings at its landing site inside Gale Crater. The rim of Gale Crater can be seen to the left, and the base of Mount Sharp is to the center-right.
A partial view of a 360-degree color panorama of the Curiosity rover's landing site on Gale Crater. The panorama comes from low-resolution versions of images taken Thursday, August 9, with a 34-millimeter mast camera. Cameras mounted on Curiosity's remote sensing mast have beamed back fresh images of the site.
NASA's Curiosity rover took this self-portrait using a camera on its newly deployed mast.
A close-up view of an area at the NASA Curiosity landing site where the soil was blown away by the thrusters during the rover's descent on August 6. The excavation of the soil reveals probable bedrock outcrop, which shows the shallow depth of the soil in this area.
This color full-resolution image showing the heat shield of NASA's Curiosity rover was obtained during descent to the surface of Mars on Monday, August 13. The image was obtained by the Mars Descent Imager instrument known as MARDI and shows the 15-foot diameter heat shield when it was about 50 feet from the spacecraft.
This first image taken by the Navigation cameras on Curiosity shows the rover's shadow on the surface of Mars.
The color image captured by NASA's Mars rover Curiosity on Tuesday, August 7, has been rendered about 10% transparent so that scientists can see how it matches the simulated terrain in the background.
This image comparison shows a view through a Hazard-Avoidance camera on NASA's Curiosity rover before and after the clear dust cover was removed. Both images were taken by a camera at the front of the rover. Mount Sharp, the mission's ultimate destination, looms ahead.
The four main pieces of hardware that arrived on Mars with NASA's Curiosity rover were spotted by NASA's Mars Reconnaissance Orbiter. The High-Resolution Imaging Science Experiment camera captured this image about 24 hours after landing.
This image is a 3-D view in front of NASA's Curiosity rover. The anaglyph was made from a stereo pair of Hazard-Avoidance Cameras on the front of the rover. Mount Sharp, a peak that is about 3.4 miles high, is visible rising above the terrain, though in one "eye" a box on the rover holding the drill bits obscures the view.
This view of the landscape to the north of NASA's Mars rover Curiosity was acquired by the Mars Hand Lens Imager on Monday afternoon on the first day after landing.
This view of the landscape to the north of NASA's Mars rover Curiosity was acquired by the Mars Hand Lens Imager on Monday afternoon, the first day after landing.
This is one of the first pictures taken by Curiosity after it landed. It shows the rover's shadow on the Martian soil.
Another of the first images taken by the rover. The clear dust cover that protected the camera during landing has popped open. Part of the spring that released the dust cover can be seen at the bottom right, near the rover's wheel.
This image shows Curiosity's main science target, Mount Sharp. The rover's shadow can be seen in the foreground. The dark bands in the distances are dunes.
Another of the first images beamed back from NASA's Curiosity rover on August 6 is the shadow cast by the rover on the surface of Mars.
NASA's Mars Curiosity Rover, shown in this artist's rendering, touched down on the planet on August 6, 2012.
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