This is it, folks. After traveling for more than eight months, over a distance of 350 million miles, NASA's one-ton, nuclear-powered, six-wheel drive rover, Curiosity, is just hours away from touching down on the surface of the Red Planet.
It won't be easy. Curiosity's entry, descent and landing — called "EDL" by NASA engineers — is the most ambitious the Agency has ever attempted. From the top of the atmosphere to the surface of the planet takes just seven minutes, but it will involve slowing the rover from over 13,000 miles per hour to a complete, safe, and total stop on Martian terrain. It takes light 14 minutes to make the trip from Earth to Mars, which means controlling the spacecraft directly from Earth is out of the question; Curiosity has been programmed to perform all of its EDL maneuvers autonomously. If it works, it works. If it doesn't... well...
Let's not worry about that. For now, let's get geared up for one of the most historic nights in the history of space exploration.
18:43 PT | Distance from Mars: 32,680 miles | Time to Touchdown: 3:48:11
First things first: here's the livefeed from NASA — when word comes down that Curiosity has reached the surface of the planet safely (or not), this is where you'll hear it first. We'll start our commentary at 20:00 PT.
20:02 PT | Distance from Mars: 21,918 miles | Time to Touchdown: 2:28:36
Curiosity is currently streaking toward Mars at 8,687 miles per hour. It will continue to pick up speed in the hours ahead, thanks to the force of Martian gravity, ultimately entering the planet's atmosphere in excess of 13,000 miles per hour. That's around twenty times the speed of a bullet.
20:12 PT | Distance from Mars: 20,665 miles | Time to Touchdown: 2:19:28
NASA recently released an awesome interactive animation depicting the stages of Curiosity's entry, descent and landing, or "EDL" — click here to check it out. It's a great overview of the landing procedure, and includes lots of cool stats, like how fast the rover will be moving at various altitudes during its seven-minute trip from the top of the atmosphere to the surface of the planet.
20:27 PT | Distance from Mars: 18,600 miles | Time to Touchdown: 2:04:30
There are scientists and engineers at NASA who have devoted as much as a decade of their lives to the Curiosity project. Tonight, all that work will be put to the test. In an interview with io9, NASA JPL systems engineer Devin Kipp said he was feeling "excited, anxious and petrified" all at once. Everyone is going through "alternating emotions," he said.
His sentiments resonate with those of Scott Hubbard, former director of NASA's Ames Research Center, who described the atmosphere around NASA and JPL as follows:
"Everybody is on edge. There's a lot of confidence there, but the truth is Mars is still mostly an unknown. It's a tense confidence."
As Adam Steltzner, leader of Curiosity's descent and landing team, told reporters earlier today: "We're rationally confident, emotionally terrified."
UPDATE: 20:35 PDT
@MarsCuriosity updates us on its status:
Those numbers are a little different from the ones on NASA's Eyes on the Solar System, an awesome interactive 3D simulator (screenshot featured here) that allows you to follow Curiosity's approach. Check it out for yourself here.
21:06 PT | Distance from Mars: 13,120 miles | Time to Touchdown: 1:025:00
21:12 PT | Distance from Mars: 12,300 miles | Time to Touchdown: 1:20:00
THE UPLINK TRANSMITTER IS NOW OFF. In other words: JPL is no longer giving Curiosity any instructions. "She is now truly on her own."
Curiosity is also now within the orbit of Deimos, one of Mars' moons. We're getting very, very close.
21:31 PT | Distance from Mars: 9,500 miles | Time to Touchdown: 1:00:00
We are now one hour away from Curiosity's projected touchdown.
21:33 PT | Distance from Mars: 9,200 miles | Time to Touchdown: 58:00
Fun fact: the holes in Curiosity's wheels spell out "JPL" in morse code... useful for spotting Curiosity's tracks on the surface of Mars.
21:40 PT | Distance from Mars: 8,170 miles | Time to Touchdown: 51:00
Beginning about 11 minutes, 30 seconds before entry into Martian atmo, JPL will start receiving "tones" from Curiosity, depicted here with pink dashes. These basic radio-frequency tones will go directly from Curiosity to Earth, updating us on the spacecraft's status.
These tones will continue for around 13 minutes, but we'll lose direct contact with Curiosity a couple of minutes after it enters the atmosphere, as the spacecraft loses sight of Earth over the Martian horizon. At that point, JPL will rely on UHF radio data (depicted here in blue), that will be relayed to Earth via satellites in orbit around Mars. Both the Mars Odyssey spacecraft and Mars Reconnaissance Orbiter will be overhead during Curiosity's landing. MRO's HiRISE Camera will be attemptint to snap a photo of Curiosity during its descent; Odyssey will act as a "bent pipe," relaying curiosity's UHF radio data to Earth.
21:52 PT | Distance from Mars: 6,100 miles | Time to Touchdown: 39:00
Curiosity has officially entered EDL mode in preparation for its descent. "There's no going back," says Allen Chen in JPL Mission Control.
21:57 PT | Distance from Mars: 5,270 miles | Time to Touchdown: 33:00
"I'd like to thank the cruise taem for bringing us over 350 million miles... curiosity is in fantastic shape to perform entry descent and landing, and she's there because you guys got her here. Good luck, and see you on the other side, on Mars" - Adam Steltzner, leader of Curiosity's descent and landing team.
22:01 PT | Distance from Mars: 4800 miles | Time to Touchdown: 30:00
We're now about 23 minutes to entry. Everybody at JPL is munching on peanuts for good luck:
UPDATE: 22:07 PT
Curiosity will not be in direct contact with Earth when it sets down on Mars. Instead, it will rely on Odyssey, a spacecraft in orbit around Mars, to relay information back to Earth. Odyssey will be orbiting above Curiosity when it lands, but there's still a chance it won't be able to relay information on the rover's status back to Earth on its first pass, which means we may not know if Curiosity's landed safely until a couple hours after its projected landing time.
Good news: Odyssey is where it needs to be!
However, just because Odyssey is in position doesn't mean it will be able to relay Curiosity's signal. Fingers crossed, people.
22:15 PT | Altitude: 1140 miles | Time to Atmosphere Entry: 09:00
Curiosity's Cruise stage has separated. We're less than 9 minutes to entry, and around 16 minutes away from touchdown. Curiosity has reached a velocity of 11,650 miles per hour, and she's still gaining speed. Mars is looking pretty big right now.
22:19 PT | Altitude: 599 miles | Time to Atmosphere Entry: 05:32
Just under 6 minutes. "Heartbeat tones" are Curiosity's way of telling us everything is as it should be.
We won't be able to start receiving data from Odyssey until shortly after atmospheric entry, just before Curiosity's parachute opens.
22:25 PT UPDATE: CURIOSITY HAS ENTERED MARS ATMO, traveling 13,100 miles per hour!
Cue the seven minutes of terror.