In the wee hours of Friday morning, a billion miles away, a plucky little space probe the size of a Mini Cooper and the shape of a wok began its final descent onto the surface of Titan, the largest moon of the planet Saturn.

Space scientists around the world held their breath. For many of them, including several faculty members in the Atmospheric, Oceanic and Space Sciences Department of the University’s College of Engineering, the events of the next few hours would be a culmination of decades of research, planning, and waiting.

The European Space Agency’s Huygens probe had hitched a ride on NASA’s Cassini spacecraft, attached to its side for the seven-year on route to Saturn that looped through the solar system, receiving speed boosts from the gravities of Earth, Venus and Jupiter. A few months after easing into Saturn’s orbit last July, the Huygens probe woke from its long sleep as it separated from Cassini on Christmas Day, headed for its final destination of Titan. If all went according to plan, Huygens would fulfill its mission of performing experiments on Titan’s surface and lasting for only a couple of minutes, due to the harsh conditions of the moon.

Instead, the probe lasted over three hours. While falling through Titan’s thick atmosphere, Huygens performed scientific experiments, taking in samples of the atmosphere to measure its content, mapping the surface with radar and taking photographs of Titan’s features. Onboard the Huygens is a gas chromatograph mass spectrometer, of which AOSS professor Sushil Atreya is a co-investigator. It “inhales” some of the smoggy Titan atmosphere and heats the particles to reveal their composition. Raw data from the GCMS has yet to be interpreted.

Preliminary data beamed back already reveals a complex landscape — plateaus, floodplains and lakes of liquid hydrocarbons. “We see drainage canals, stubby canyons and shorelines. We’ve suspected these, but have never seen them like this,” said Martin Tomasko, a planetary scientist at the University of Arizona, in a NASA interview.

With the success of the engineering component of this mission — that of sending the probe to Saturn and dropping it onto Titan’s surface — the scientific investigation of the collected data is ready to begin. Over the several hours that Huygens was functioning and able to relay information back to the Cassini orbiter overhead, instruments measured the aspects of the moon that puzzled scientists and made it such a tempting target.

Scientists had long known that Titan contained great amounts of simple hydrocarbons — the precursor molecules, such as methane, that life arose from on Earth. Being so cold and so far away from the Sun, however, Titan seemed unlikely to harbor life. Instead, NASA and ESA hoped to find a snapshot of conditions on the early Earth, frozen in time. Titan is also the only moon in the solar system known to have its own atmosphere.

On Earth, scientists at the ESA’s command center in Darmstadt, Germany, had to wait the 59 minutes it took for data beamed from Saturn to travel all the way back home. Around the globe, astronomers scrambled to point their radio observatories to catch the faint signal directly from Huygens and the stronger signal relayed by Cassini. In Australia, China, Japan and the United States, as one hemisphere of the Earth rotated out of sight of the probe, radio observatories in the other picked up the signal.

Involving hundreds of scientists from 17 countries, the international collaborative effort of this successful mission was greatly emphasized. “The teamwork in Europe and the USA, between scientists, industry and agencies, has been extraordinary and has set the foundation for today’s enormous success,” said Jean-Jacques Dordain, ESA’s director general, at a press conference imm ediately following news of Huygen’s safe landing.

“All of those international partnerships have culminated in this one moment in history,” said an emotional NASA leader.

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