In 2005, an international team sent a probe called Huygens down to the surface of Saturn's moon Titan. This is a moon with a thick atmosphere, and which we now know has lakes, sand dunes, salt flats, and seasonal rains (of liquid methane). At the time, however, we'd never seen its surface below cloud cover. Here's what it looked like as it came into view.
This video is reconstructed from data that came in from several instruments as the Huygens probe fell through Titan's atmosphere. Best of all, at least for us humans with our eyes, are the cameras that were busily mapping as much as they could of Titan's mysterious surface. There is something timeless and breathtaking about watching the land masses of the moon slowly resolve as the probe falls through the cloud cover and, at last, lands on the ground.
According to NASA, which provided the camera to the ESA-funded Huygens probe:
The almost four-hour-long operation of the camera is shown in less than five minutes. That's 40 times the actual speed up to landing and 100 times the actual speed thereafter.
The first part of the movie shows how Titan looked to the camera as it acquired more and more images during the probe's descent. Each image has a small field of view, and dozens of images were made into mosaics of the whole scene.
The scientists analyzed Huygens' speed, direction of motion, rotation and swinging during the descent. The movie includes sidebar graphics that show:
Sounds from a right speaker go with the Descent Imager/Spectral Radiometer activity. There's a continuous tone that represents the strength of Huygens' signal to Cassini. Then there are 13 different chimes - one for each of instrument's 13 different science parts - that keep time with flashing-white-dot exposure counters. During its descent, the Descent Imager/Spectral Radiometer took 3,500 exposures.
- (Lower left corner) Huygens' trajectory views from the south, a scale bar for comparison to the height of Mount Everest, colored arrows that point to the sun and to the Cassini orbiter.
- (Top left corner) A close-up view of the Huygens probe highlighting large and unexpected parachute movements, a scale bar for comparison to human height.
- (Lower right corner) A compass that shows the changing direction of view as Huygens rotates, along with the relative positions of the sun and Cassini.
- (Upper right corner) A clock that shows Universal Time for Jan. 14, 2005 (Universal Time is 7 hours ahead of Pacific Daylight Time). Above the clock, events are listed in mission time, which starts with the deployment of the first of the three parachutes.
Sounds from a left speaker trace Huygens' motion, with tones changing with rotational speed and the tilt of the parachute. There also are clicks that clock the rotational counter, as well as sounds for the probe's heat shield hitting Titan's atmosphere, parachute deployments, heat shield release, jettison of the camera cover and touchdown.
Huygens arrived at Titan on NASA-JPL's Cassini probe, taking thousands of pictures and readings of Saturn, many of which are still being analyzed today.