Cassini in mission's final week

The spacecraft will plunge into Saturn by the end of the year.
By Laurel Kornfeld | Sep 12, 2017
NASA's Cassini spacecraft entered its final week with the last of 22 dives between Saturn and its rings on Saturday, September 9.

In orbit around the giant planet since 2004, Cassini is running out of fuel. As done with the Galileo Jupiter probe, NASA decided to destroy the spacecraft by crashing it into Saturn's atmosphere, where it will be torn apart.

Because the probe has so little fuel left, scientists decided to end the mission this way to avoid the spacecraft someday impacting one of Saturn's moons, at least two of which are potentially habitable for microbes.

Even though Cassini was sterilized before launching from Earth in 1997, it is possible some microbes survived on the spacecraft. These could contaminate the habitable moons and be wrongly identified by future missions as life indigenous to those worlds.

Scientists believe some bacteria can survive up to 20 years in space.

Among Cassini's discoveries are powerful hurricanes at Saturn's poles, with sizes up to 50 times that of hurricanes on Earth, noted mission project scientist Linda Spilker of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

The giant planet's north pole hosts strange, hexagon-shaped jet streams found nowhere else in the solar system.

Cassini's 22 Grand Finale dives between Saturn and its rings have revealed surprising features. In some parts of the rings, the tiny particles that make them up clump together while in other parts, the particles float alone in space.

Before the plunge into Saturn, mission scientists hope Cassini's magnetometer, which measures the planet's magnetic field, will discover a telltale tilt in that field from which they can derive the exact length of a Saturn day, something that remains unknown even now.

Among Cassini's major findings are the potential habitability of Saturn moons Enceladus and Titan.

Large geysers coming from Enceladus' south pole suggest the presence of a subsurface liquid ocean that could possibly host microbial life.

The probe's composite infrared spectrometer revealed the small moon to have a porous surface.

On the much larger Titan, Cassini and its Huygens lander observed lakes of ethane and methane and atmospheric clouds.

Prepared for all contingencies, the spacecraft is equipped with two computers, two star scanners, two Sun sensors, two gyroscopes, and two radios.

One day before impacting Saturn, Cassini will conduct high-resolution observations of the planet's temperature, auroras, and vortices, take closeup images of the north pole hexagonal jet stream, and image Titan and Enceladus.

Radio contact with Earth will be lost within approximately two minutes of the probe's entrance into Saturn's atmosphere.


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