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Rest in space: In loving memory of Cassini, 1997-2017

NASA's mission to Saturn did some of the coolest space science in the history of the solar system. Here's why the plucky probe now has to die.

NASA

By the time you read this, NASA's Cassini spacecraft will be but a memory – vaporized into nothingness 1.2 billion kilometres from home. But dry your tears: Scientists will be poring over its nearly 20-year-life and 13-year sojourn around Saturn for years to come – including evidence pointing to the possibility of life beyond Earth.

1997 The Cassini spacecraft and its European hitchhiker, the Huygens probe, blast off from Cape Canaveral, Florida

1998-99 Cassini swings around Venus twice, taking pictures and picking up speed due to the planet’s gravity.

2004-2008 Cassini enters Saturn’s orbit and explores the planet, its moons and rings. Its 12 instruments “sniff” the chemical composition of dust and atmosphere, measure magnetic fields and snap high-res photos. The results are so spectacular the mission is extended to 2017.

2005 The Huygens probe gently parachutes off Cassini onto Saturn’s moon Titan. It beep-boops around for just 90 minutes, taking measurements and snapping pictures of orange sky and pebbly landscape. No spacecraft has landed farther from Earth.

2006 Cassini sees the moon Titan’s hazy atmosphere of methane, the same hydrocarbon gas found in human farts. Titan has a methane cycle like Earth’s water cycle, with methane oceans, methane clouds and methane rain.

2006-2014 Water vapour and salt are seen spewing from geysers on the moon Encedalus, supplying raw material for one of the rings. Cassini later analyzes Encedalus’s ice grains and scientists conclude they came from a vast, warm, salty, subsurface ocean of liquid water.

2013 Cassini captures a high-res movie of Saturn’s polar hexagon: a six-sided jet stream churning at the planet’s north pole. As Saturn’s year progresses (it’s 30 Earth-years long) , the sunlight changes and the vortex changes colour from blue to golden.

2016 Of the millions of dust grains  Cassini samples around Saturn, it finds 36 that appear to be from beyond our solar system. Interstellar dust moves faster and in different directions than domestic stuff.

WHY CASSINI MUST DIE
To protect the precious alien life that might lurk on Saturn’s moons — or could one day — Cassini is sacrificing itself for the sake of science. The plucky little probe found water on one of Saturn’s moons and organic soup on another. Left to sputter out on its own, it could crash into one of those worlds and pollute it with Earth germs, introducing the worst invasive species ever. So NASA decided it had to pilot Cassini directly into Saturn, letting it orbit closer and closer until it gets pulled into the planet itself. It spent its final few months exploring “Big Empty,” the gap between the planet and rings. Its last little bit of fuel will be used up in an effort to keep its antenna pointed at Earth for as long as possible as it trasmits data on Saturn’s low-lying clouds. Then it will nosedive, dish-downwards, losing contact with Earth forever. Shortly after, it will burn up and become part of the gaseous planet it so dutifully studied for 13 years.

SCIENCE STORY: Titanic Life

NASA scientists recently discovered a chemical on Saturn’s moon Titan that points to its potential for harbouring life. It’s called acrylonitrile, a.k.a. vinyl cyanide, and it’s possible that under the right conditions, it could assemble into hollow spheres surrounded by thin, flexible membranes. It’s hypothesized that a similar process took place on Earth to create the membranes in our cells.

SOUND SMART: Magnetosphere

DEFINITION
The magnetosphere is the area around a planet affected by that planet’s magnetic field.

USE IT IN A SENTENCE
Earth’s magnetosphere should be called the mag-NEATO-sphere because its collision with particles from the sun creates the northern lights.

Watch Metro Science - Live! Citizen Scientist columnist Genna Buck will be on Facebook.com/MetroCanada on Sept. 15 at 12 p.m., getting SO EXCITED about Cassini and other exciting science stories of the week. Plus she will answer a reader question about whether women have super-smelling powers at a certain point in their menstrual cycle. Tune in to find out!

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