In the wee hours of Monday morning (late on Sunday night on the West Coast), a one-ton robot the size of a Mini Cooper will land on Mars. After the Mars Science Laboratory endures its seven minutes of terror beginning at 1:31 a.m. Eastern time on August 6, the Curiosity rover begins a primary mission that will last for about 90 Martian days, or sols—but hopefully an overall journey of exploration that lasts for several more years.
Where to start when you're driving a lonely lander on a big, empty planet? The Curiosity engineers' first duty after landing will be to assess the position of the lander. Maybe it's on a rock. Maybe it's in a ditch. NASA won't know how Curiosity has landed until the first bits relayed from Odyssey and MRO (the orbiters that will help Curiosity communicate with Earth) transmit some basic data. (For us impatient space fans, the low-resolution, hazard-avoidance cameras, also known as hazcams, will offer the first insights into where Curiosity landed. The images will be black-and-white thumbnails of a new world, a Martian teaser.)
Hopefully, Curiosity comes down somewhere in the 96-mile-wide Gale Crater, its target landing spot. Gale Crater was selected due to its layers of rock that will help reveal the history of Mars's environment, similar to the striations in our earthly Grand Canyon. Every layer is a step back in Martian time, which is how the 300 members of the MSL science team, led by geologist John P. Grotzinger, will begin to pursue their main objectives. This list reads a little dry, but its contents—"Inventory the chemical building blocks of life;" "Determine present state, distribution, and cycling of water and carbon dioxide"—mean that they're after the story of Mars' past and the clues to whether it was ever home to life.
To find out, the lander is equipped with 10 scientific instruments and 17 cameras. Curiosity's exploration kit starts with the innovative ChemCam to find promising samples. This particular tool in Curiosity's arsenal can collect data about the composition of Martian rocks by shooting lasers at them. The tool concentrates the power of one million light bulbs on an area the size of a pin, then takes a photo of the plasma it creates. The camera captures the image and can analyze the sample's composition.
After Curiosity's opening checkup is complete, which should take around a week, it can begin its journey up a 3.4-mile-high mountain called Mount Sharp (also known as Aeolis Mons) in the middle of the Gale Crater, studying samples with the ChemCam as it goes. It will also pick up soil with its scoop and drill into rock to collect samples, then clean them off with its Dust Removal Tool (you may know it as a brush). The lander has its own compact chemistry lab aboard, called SAM (or Sample Analysis at Mars). SAM can analyze the samples to look for evidence of organic or carbon-based molecules. Finding these organics, is key to understanding if Mars is—or was—habitable.
Another tool called the Radiation Assessment Detector will measure radiation levels on the Red Planet, with an eye toward determining the dangers for future human explorers. Curiosity also carries DAN (Dynamic Albedo of Neutrons, which measures hydrogen), APXS (Alpha particle X-ray spectrometer ), CheMin (Another spectrometer that analyzes samples for mineral composition) and more.
One of the key challenges for Grotzinger as the Curiosity mission goes on will be deciding which instruments and experiments get priority, as 300 scientists all want to learn something different about Mars. A researcher from Canada, for instance, wants to point the laser in ChemCam at the sky to learn more about the Martian atmosphere. The laser wasn't built specifically for that purpose but a lot can be learned from the experiment. Everyone agrees this is cool. But when will it get slotted in? The atmospherics guys are probably a lot more excited about seeing fog and ice crystals than the geologists.
The good news is that just arriving on Mars is half the battle. As with most things in the universe, the first step is the hardest.