"Deep Impact" released 1998

One of two comet/asteroid disaster movies to hit theaters, Deep Impact, opened May 8, 1998.  A seven-mile wide comet is on a collision course with Earth, and the world prepares for a mass extinction.

Steven Spielberg was executive producer.  It starred Robert Duvall, Tea Leoni, Elijah Wood, Maximillian Schell, Morgan Freeman, James Cromwell, Jon Favreau, Denise Crosby (of Star Trek: The Next Generation fame), and Blair Underwood.

The movie is based on the 1993 novel The Hammer of God by Arthur C. Clarke.  

Chiron, minor planet, discovered 1977

Chiron, a minor planet between Saturn and Uranus, was discovered November 1, 1977, by Charles Kowal.  It was the first of a class of objects known as centaurs, astral bodies orbiting between the asteroid belt and the Kuiper Belt.  

It also has a classification as a comet, 95P/Chiron.

It has a radius of about 107.8 + 5km and rotates about every 6 hours.  It orbits the sun about every 50.5 years.

In February 1988, it brightened by 75%, which is typical of comets but not asteroids.  In April 1989, it developed a cometary coma, and in 1993, it formed a tail.  

Stardust Sample Return Capsule lands 2006

The Sample Return Capsule from the Stardust space probe on January 15, 2006 and landed safely in Utah.  Stardust had made a flyby of the comet Wild 2 and taken samples of dust from the coma of the comet.

Among the many compounds discovered was glycine, an amino acid that scientists identify as a fundamental chemical building blocks of life.  Scientists at the University of Arizona confirmed the presence of liquid water in Wild 2.

Comet Howard–Koomen–Michels collides with Sun 1979

Comet Howard-Koomen-Michels, a sungrazer comet, collided with the sun August 30, 1979.  At the time, it was the only know comet to crash into the sun since most comets are vaporized before they make contact with the solar surface.  It is also the first comet to be discovered by a spacecraft.

This probably isn't Comet Howard-Koomen-Michels but it is a good video of a comet colliding with the sun.

Stardust encounters comet Wild 2 2004

Comet Wild 2 as seen from Stardust

NASA's Stardust spacecraft encountered the comet Wild 2 January 2, 2004.  That's pronounced "vilt" since it was named after Paul Wild, the Swiss astronomer who discovered it in January 1978 and that's how his name is pronounced.

Stardust was launched in February 1999 to collect dust samples from the coma of the comet, but it also flew by and studied asteroid 5535 Annefrank.

The Sample Return Capsule separated from Stardust and entered Earth's atmosphere January 2006.  Samples from Wild 2 were sent to Johnson Space Center in Houston for analysis.  Scientists announced that glycine, an amino acid which is a fundamental chemical in building blocks of life, was detected for the first time in material ejected from a comet.

Stardust was given an extension and made a flyby of comet Tempel 1 in February 2011, although no samples were collected.  The spacecraft was decommissioned March 2011.

Chiron discovered 1977

Chiron, an asteroid/minor planet/comet/centaur/whatsit, was discovered by Charles Kowal November 1, 1977 from images taken October 18 from the Palomar Observatory in southern California.  It may have been observed as far back as 1895.

At first, Chiron (named after the wisest and justest centaur from Greek mythology) was classified as a minor planet because its orbit lay between Saturn and Uranus, much further than the asteroid belt.  Subsequently, its classification was downgraded to an asteroid. 

Then in 1988, it brightened by 75% which is characteristic of comets, but not asteroids.  In 1993, a tail was discovered so NASA thought it was a comet.  So they decided, why not classify it as both a comet and a minor planet.  Chiron is officially known as a centaur, a dual classification of comet and minor planet, orbiting between the asteroid belt and the Kuiper belt.




https://en.wikipedia.org/wiki/2060_Chiron

Rosetta spacecraft's mission has ended

One of the last images of Comet 67P/Churyumov-Gerasimenko taken by Rosetta

The European Space Agency's Rosetta spacecraft has ended its mission with an impact on the Comet 67P/Churyumov-Gerasimenko. Rosetta was launched in 2004 and reached the comet August 2014.  Two months later, Rosetta deployed Philae, the small lander, which made an unceremonious landing on the comet.  It took the first pictures ever of the surface of a comet.

ESA decided not to continue Rosetta's mission as the comet heads out beyond the orbit of Jupiter.  For one, the sun will be in the line of sight between Earth and Rosetta, making communications with the spacecraft difficult.  Also, there would be little power to operate the spacecraft.

The mission has been considered a major success.

It's official! Comets contain booze and sugar!

Comet Lovejoy

Researchers at the Paris Observatory, using a 30-meter radio telescope in Sierra Nevada, Spain took measurements of Comet C/2014 Q2 (aka Comet Lovejoy) in January 2015 when it was at its brightest.  Among the 21 compounds the scientists found were ethanol and glycolaldehyde, simple sugar.  Researchers studying data from the Rosetta mission claim they have found the same molecules on Comet 67P/Churyumov-Gerasimenko (aka Comet 67P).

Comet 67P/Churyumov-Gerasimenko

The Parisian scientist also detected ethylene glycol, formic acid and acetaldehyde, which have been discovered on Hale-Bopp and other comets.  The Philae lander has detected methyl isocyanate, acetone and acetamide which have not been reported in other comets.  Philae found more organic molecules, some containing nitrogen.

Since comets contain some of the oldest material in the solar system, they might explain how the substances for life were brought to Earth.  In 2009, the Stardust mission, which flew by Comet Wild 2 in 2004 and returned to earth, brought back samples which contained glycine, a simple amino acid.  It is still unknown how it got onto the comet but more complex molecules could be formed when an amino acid-carrying comet made impact with the Earth's surface.

Comet Wild 2

Comets might also demonstrate how planes were formed during the sun's youth.

https://www.newscientist.com/article/dn28382-booze-and-sweets-officially-found-in-nearby-comet-for-first-time/

http://www.sciencemag.org/content/349/6247/aab0689.full?ijkey=FnbUvge85XZ9Y&keytype=ref&siteid=sci

https://www.newscientist.com/article/dn17628-found-first-amino-acid-on-a-comet

After 10 years, Rosetta catches up with a comet

Launched back in 2004, the European Space Agency's probe Rosetta has rendezvoused with Comet 67P/Churyumov-Gerasimenko, somewhere between the orbits of Mars and Jupiter.  Sometime in November, Rosetta plans to place the lander Philae on the comet's surface! Until then, she's going to observe the comet from about 100 km, the closest a probe has been to a comet, to find the best spot for Philae.

Comet 67P/Churyumov-Gerasimenko

Back in 1978, the International Sun-Earth Explorer was launched, did its job and then was deactivated.  It was reactivated in September 1985 and diverted through the tail of Comet Giacobini-Zinner, over 4700 miles from the core and then Halley's Comet in 1986 at a distance of 31 million kilometers.  In March 1986, ESA's Giotto flew within 600 km, taking the closest pictures of a comet at that time.