Starship Asterisk*

BDanielMayfield wrote: ↑Sun Mar 31, 2019 4:20 am

orin stepanek wrote: ↑Sat Mar 30, 2019 3:10 pm
Not a whole lot of vapor coming from this comet; must be a low moisture comet!

It's not so much that it's a dry comet, but that it only gets close enough to the sun for a light steaming. But its water is extra heavy:

The ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water. NASA reported that, between June and August 2014, the comet released increasing amounts of water vapor, up to tenfold as much.

orin stepanek wrote: ↑Sun Mar 31, 2019 12:54 pm
I wonder how much rain we get because of comets?

https://en.wikipedia.org/wiki/Leonids wrote:

A famous depiction of the 1833 meteor storm, produced in 1889 for the Seventh-day Adventist book Bible Readings for the Home Circle.

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<<The Leonids are a prolific November meteor shower associated with the comet Tempel–Tuttle, which are also known for their spectacular meteor storms that occur about every 33 years. Their proper Greek name should be Leontids but the word was initially constructed as a Greek/Latin hybrid and it has been used since.

Earth moves through the meteoroid stream of particles left from the passages of a comet. The stream comprises solid particles, known as meteoroids, ejected by the comet as its frozen gases evaporate under the heat of the Sun when it is close enough – typically closer than Jupiter's orbit. The Leonids are a fast moving stream which encounter the path of Earth and impact at 72 km/s. Larger Leonids which are about 1 cm across have a mass of half a gram and are known for generating bright (apparent magnitude −1.5) meteors. An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.

The Leonids are famous because their meteor showers, or storms, can be among the most spectacular. Because of the storm of 1833 and the recent developments in scientific thought of the time, the Leonids have had a major effect on the development of the scientific study of meteors, which had previously been thought to be atmospheric phenomena. Although it has been suggested the Leonid meteor shower and storms have been noted in ancient times, it was the meteor storm of 1833 that broke into people's modern day awareness – it was of truly superlative strength. One estimate of the peak rate is over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of 240,000 meteors during the nine hours of the storm, over the entire region of North America east of the Rocky Mountains.

It was marked by several nations of Native Americans: the Cheyenne established a peace treaty and the Lakota calendar was reset. Abolitionists including Harriet Tubman and Frederick Douglass took note and others. Abraham Lincoln commented on it years later.

Denison Olmsted noted the shower was of short duration and was not seen in Europe, and that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space. Accounts of the 1866 repeat of the Leonids counted hundreds per minute/a few thousand per hr in Europe. It was in 1866–67 that information on Comet Tempel-Tuttle was gathered pointing it out as the source of the meteor shower. When the storms failed to return in 1899, it was generally thought that the dust had moved on and storms were a thing of the past.>>

orin stepanek wrote: ↑Sat Mar 30, 2019 3:10 pm Not a whole lot of vapor coming from this comet; most be a low moisture comet!

Like the other comets of the Jupiter family, Churyumov–Gerasimenko probably originated in the Kuiper belt and was ejected towards the interior of the Solar System, where later encounters with Jupiter successively changed its orbit.

Up to 1840, the comet's perihelion distance was 4 AU (600 million km), too far for the Sun to vaporize the nucleus. In 1840 Jupiter changed the orbit to a perihelion distance of 3 AU (450 million km), and later encounters further decreased that distance to 2.77 AU (414 million km).[43]

In February 1959, a close encounter with Jupiter[44] moved Churyumov–Gerasimenko's perihelion inward to about 1.29 AU (193 million km), where it remains today.[14][43]

The composition of water vapor from Churyumov–Gerasimenko, as determined by the Rosetta spacecraft, is substantially different from that found on Earth. The ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water. This makes it unlikely that water found on Earth came from comets such as Churyumov–Gerasimenko.[9][63][64] On 22 January 2015, NASA reported that, between June and August 2014, the comet released increasing amounts of water vapor, up to tenfold as much.