Farewell, Cassini, the little probe that could!

Just before 8am EDT today, Cassini, the spacecraft sent to study Saturn and her moons, sent her last signal.  She plunged into the Saturnian atmosphere to end a massively successful mission.  Launched October 15, 1997, she spent Cassini spent 7 years en route and arrived at Saturn in 2004.  For 13 years, she has explored the gas giant and released the Huygens probe from the ESA to land on Titan, a first for a celestial body in the outer solar system.

Cassini did flybys of Jupiter, our moon and Asteroid 2685 Masursky.  She discovered new moons Methone, Pallene, Polydeucesin, Daphnis, Anthe, Aegaeon and S/2009 S 1.  I'm sure they will find a better name for the last one.

She also performed flybys of moons Titan, Phoebe, Enceladus, Iapetus, Rhea, Hyperion and Dione.

Seventeen countries joined together in this effort.

Cassini dives into Enceladus' plume

Two days ago, the Cassini spacecraft completed its deepest dive ever toward Saturn's moon, Enceladus.  The probe passed over the south polar region at a distance of only 30 miles.  During the flyby it took samples of the plumes which have been observed on Enceladus for years.  It'll take several weeks to complete the analyses but it should give researchers some clues to the composition of the global ocean beneath the surface. 

On its next and final flyby in December, Cassini will measure the amount of heat coming from the moon's interior.  Enceladus could be a future target for exploration in search of habitable environments beyond Earth.

Cassini-Hugyens spacecraft launched in 1997

The Cassini-Huygens space probe, now circling Saturn and her moons and sending back tons of data, started its seven year trek on October 15, 1997.  It arrived at the planet in June 2004 for a four year mission, which it completed in 2008 however it is still going strong.  It has sent back hundreds of gigabytes of data on Saturn, Titan, Enceladus, Iapetus, Dione, Hyperion, Tethys and other moons.

Starting this week, Cassini will make three close encounters with Enceladus.  She will fly through the icy material continually erupting from the moon's surface.  A tricky maneuver, given the speed of the probe and what damage even a small particle can do.

Part of the mission was to deploy the Huygens lander on the surface of Titan.  It landed with little difficulty and transmitted about 90 minutes after touchdown.  Images show an orange surface covered with hydrocarbon-coated water ice pebbles.  The temperature was a balmy -179.35 °C!  It's the farthest surface landing from Earth.

Science news this week: Europa, Mars and a Super-Moon!

When Voyager 2 flew past the Jovian moon Europa in 1979, Earthlings received images of a flat white surface, no craters, just mysterious brown streaks across the moon’s exterior.  The lack of features meant some force was present to erase the evidence of asteroid impacts.  I even remember reading news reports saying the closer Voyager 2 got to Europa, the younger the moon looked.  In fact, according to Popular Science, the discoveries prompted Arthur C. Clarke to write a sequel to his highly successful 2001: A Space Odyssey.  In his novel 2010, they beings warned the Earthlings, “all these words are yours – except Europa.  Attempt no landing here.”  Author Corey S. Powell reports that this warning has become a in-joke and a taunt to scientists.

Last week, NASA reported a huge global sub-surface ocean on the Saturnine moon Enceladus but this week they reported Europa as being the wettest known world in the solar system with more than twice the water on earth.  Life needs water.  Everywhere water exists on Earth so does life.  So to find alien life, one must look for alien water.  Europa has about 3 million cubic kilometers of it.

Life also needs good and energy, which Europa also contains.  Scientists suggest the oceans could be ‘nourished by a drizzle of organic chemicals’ stirred by volcanic vents.

Proving it will be a task worthy of Jupiter himself.  It’s about 600 million miles from here to Europa and that could take about 6 years.  The surface of the moon receives an average radiation dose of 500 rem/day, which can fry unshielded electronics in just a few days.  Lastly, the ice shell is about 10 miles thick, much more than the ice covering the Antarctica.  Many scientist are saying we should try, though.

The last probe to visit Jupiter and her moons was Galileo in 1995 and lasted until 2003 when the mission ended.  In May this year, NASA began developing a probe to visit Europa sometime in the 2020’s.

We might never find out what is below the surface of Europa unless we ignore the warnings of Arthur C. Clarke and put a lander on it.

 

In other news this week, it has been one year since NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) entered orbit above the Red Planet. Among its objectives, MAVEN will try to figure out where the water went.

 

 

Gases escaping from Mars:

And don’t miss the lunar eclipse with a Super-Moon, this Sunday, Sept 27.

Saturnine moon Enceladus has global subsurface ocean

 

For the past ten years, the scientists at NASA have been studying data from the Cassini space probe in orbit above Saturn.  Launched October 15, 1997, the orbiter named after Italian astronomer Giovanni Cassini, reached its destination in mid-2004.  Since then, the probe has been collecting and sending data on Saturn’s atmosphere and rings, Titan’s atmosphere, Iapetus and Enceladus.

Researchers noticed a slight wobble in Enceladus, the sixth largest moon, as it orbited Saturn.  According to Carolyn Porco, the scientist leading the exploration of Enceladus, members of her team looked for a libration, a “small, cylindrical, back and forth deviation from uniform rotation”. They found what they were looking for but only in the thin, outer ice shell.  This means the shell and the rocky core are separated by a liquid layer and it is global.  Had the core and the ice shell been connected, the wobble would have been much less.

Why isn’t this liquid layer frozen? 

Scientists noticed plumes rising from the surface of Enceladus as early as 2005 and subsequently discovered icy ‘material’ emerging from warm fractures near the south pole.  They suggest hydrothermal activity is occurring on the subsurface ocean floor.

However, the pull of Saturn’s gravity might be generating more heat within Enceladus, which could also explain why the liquid layer is not frozen.

On October 28, Cassini is scheduled to fly only 30 miles above the surface of Enceladus, its closest approach ever, through the plumes of icy material.  Perhaps it will confirm the presence of organic material, the building blocks of life.