Mohawk Valley Astronomical Society

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Silence is Golden

by Perry Pezzolanella

On January 14, 2005, a spacecraft descended through a smoggy atmosphere of mystery and excitement oblivious to its fate far below. Would it splash into an inky black sea, splat onto mud, plop onto a sand dune, or end up crashing into a mountain or tumbling down a cliff? The dramatic scenery that unfolded as soon as it descended below the smog, about 12 miles above the surface, blew away all imagination.

Huygens was a probe built by the European Space Agency (ESA) that was attached to the Cassini spacecraft which arrived in orbit around Saturn on June 30, 2004. It was released on December 24 that year and quietly fell towards Titan on a long looping arc. A heat shield protected it as it entered Titan’s thick atmosphere. Once the danger passed, it was ejected and a large parachute was deployed. It sampled the atmosphere 89 miles above the surface in the murk and detected a lone possible lightning static. It then released the large parachute and descended on a smaller one so it could make it to the surface faster in order to have enough battery life left to operate. What emerged from beneath the smog was an eerily Earth-like scenery bathed in a dim golden-orange daylight due to the thick atmosphere. Low mountains faded into the distant haze and far below were branching riverbeds draining into what looked like a dark sea. Low fog appeared to hug the shoreline and it was not difficult to imagine the sound of surf crashing along the shore while the wind howled all around. Unfortunately, Huygens descended in silence as there was no sea or crashing waves below. Huygens landed almost in a splat onto a vast mudflat with the consistency of wet sand or dense, wet snow. There was evidence that liquid methane/ethane had flowed and ponded there very recently, maybe only days ago. The water-ice rocks and pebbles around the spacecraft were rounded providing strong evidence of flowing liquid. The sounds of a babbling or gurgling stream were not far from reality as Cassini soon discovered great methane/ethane seas near Titan’s north pole, and observed sudden dramatic storm clouds develop, waves on the seas, and lake effect clouds.

Huygens collected data for 72 minutes from Titan’s surface in the numbing -290ºF cold and took about 100 pictures of the same slice of terrain which looked like a vast pebble-strewn beach. The atmospheric pressure was confirmed to be 1.6 times Earth’s. The rivers Huygens saw while descending showed drainage channels similar to Earth with small channels feeding into larger rivers and emptying out into flat deltas. Bright highlands showed rough, jagged terrain. Steep river valleys prone to flooding showed signs of methane rain erosion. There was evidence that liquid methane welled up through the ground creating gentle streams. Huygens landed in a damp environment with a drop of methane condensing onto the warm spacecraft as proof. This was the first proof of liquid on another world.

Huygens was only a small part of the Cassini mission and had a brief life, but it yielded big science that is still being analyzed nearly 17 years later. It remains the only spacecraft to land on a moon besides Earth’s, the only spacecraft to land on a surface of a world beyond the asteroid belt, and took the most distant photo from the surface of a world. In 2034, the silence will be broken with the sound of whirring rotors when a drone called Dragonfly begins exploring the magnificent Earth-like wonders of Titan bathed in a golden-orange hue.