Dirty Snowballs

[MrGamma]

Is this for real?

 

Scientists in 1997 claimed that the earth was being bombarded with upto 43,000 dirty snowball comets a day.

 

"Tiny Comets May Have Huge Impact"

http://query.nytimes.com/gst/fullpage.html?res=9505E7DD123AF93AA15756C0A961958260&sec=&spon=&pagewanted=all

 

I'll admit... it's getting really hard to find the truth... the only reason why I thought the whole dirty snowball thing was a fake was because NASA has a stardust program which says comets are not made of dirty snow...

 

"Stardust Findings Suggest Comets More Complex Than Thought"

http://stardust.jpl.nasa.gov/news/news110.html

 

If anybody could help me keep my sanity for a bit and possibly shed some light on this story ( perhaps it has a history ) then it would be appreciated.

 

Are comets really pummeling the earth with dirty snow? If they are not...

 

How does something like this make the New York Times?

[D H]

First off, the New York Times article was written in 1997. Stardust brought its samples back to Earth just a couple of years ago or so. The Times would have to have trained their reporters to be time travellers for them to have incorporated 2006 results in a 1997 article. The Times might be good, but I don't think they're that good.

 

Secondly, where is the contradiction? Stardust was designed to collect particulate matter from Comet Wild 2. Water is a volatile material; Stardust was not designed to collect it. It was designed to collect the "dirty" part of the dirty snowball.

[MrGamma]

First off, the New York Times article was written in 1997. Stardust brought its samples back to Earth just a couple of years ago or so.

 

This I realize... What baffles me is that the New York times article claims that up to 43,000 dirty snowballs are pummeling the earth each day...

 

I know when you look at a comet from a distance it appear to be an "ice ball" but for the most part it's accretion matter from it's travels... or so they say (NASA StarDust)...

 

I'm just freaked out that this many "ice balls" have been seen flying into the atmosphere each day... Is this a real phenominon or an imagined one?

[insane_alien]

its real, a couple thousand tonnes of stuff gets deposited into the atmosphere every day. most just burns up around 60km above the surface and one or two chunkier bits will make it to the ground but will just be falling like you dropped them off a plane because the energy gets taken out of them high up.

 

you don't have to start worrying till they're a few tens of meters across.

[D H]

I know when you look at a comet from a distance it appear to be an "ice ball" but for the most part it's accretion matter from it's travels... or so they say (NASA StarDust)...

The material gathered by StarDust does not contradict the dirty snowball model. StarDust gathered particulate matter -- the "dirty" part of the dirty snowball. Look at it this way: Suppose the comet was 99% volatiles and 1% particulates. Even then, StarDust would still have brought back particulates only and no water. It wasn't designed to collect water or look for water.

[MrGamma]

The material gathered by StarDust does not contradict the dirty snowball model.

 

It sort of does ( for the WILD 2 Samples )... I don't mean to paraphrase the article but...

 

"We have found very high-temperature minerals, which supports a particular model where strong bipolar gas jets coming out of the early sun propelled material formed near to the sun outward to the outer reaches of the solar system,"

 

Which means they are not captured ice-balls from the Kuiper belt or for the most part formed strictly of water/ice/methane. I am sure there are other comets which are... but this one examined by stardust... not so much... it's rock which was formed in extreme heat temperatures... and it has some ice on it's surface... it's more like an asteroid that's been through some cold weather rather than a dirty ice-ball...

 

its real, a couple thousand tonnes of stuff gets deposited into the atmosphere every day.

 

I am entirely aware that matter accretion occurs.... I just wasn't aware that 43,000 house size objects made of water-ice were slamming into the atmosphere daily...

[insane_alien]

Which means they are not captured ice-balls from the Kuiper belt or for the most part formed strictly of water/ice/methane. I am sure there are other comets which are... but this one examined by stardust... not so much... it's rock which was formed in extreme heat temperatures... and it has some ice on it's surface... it's more like an asteroid that's been through some cold weather rather than a dirty ice-ball...

 

as said before, they were only looking at the dirty part of it. and high temperature minerals are easily accumulated as the comet flies around in space. simply because space is dusty and in need of a good vacuuming(horrible pun most definitely intended).

 

i can roll a doughnut around on my floor and then examine the doughnut and find stuff that most definitely shouldn't be in a doughnut. same thing here(except with less furry stuff)

 

I am entirely aware that matter accretion occurs.... I just wasn't aware that 43,000 house size objects made of water-ice were slamming into the atmosphere daily...

 

yep. seeing as this has been happening for billions of years and is only going to get slower i think its safe to assume its nothing to worry about.

[D H]

Which means they are not captured ice-balls from the Kuiper belt or for the most part formed strictly of water/ice/methane.

It does not mean that at all! You are reading to much into / misreading the article, and you are completely ignoring the fact that StarDust did not and could not detect the volatile component of the comet. Nobody has said that comets are formed strictly of water/ice/methane. The dirty snowball model says comets are 70% volatiles or so. The goal of the StarDust project was to investigate what comprises the remaining 30% of a comet.

 

That said, scientists did indeed find some strange stuff in the StarDust return, and this might well force them to rethink details of cometary formation and comet structure -- but not where comets form.

 

I just wasn't aware that 43,000 house size objects made of water-ice were slamming into the atmosphere daily...

You are right to question this. While such objects are hard to see when they are in space, they are not hard to see when they enter the atmosphere. Some excerpts from http://impact.arc.nasa.gov/news_detail.cfm?ID=77

At the fall meeting of the American Geophysical Union (AGU) in San Francisco, December 8-12 1997, there were press reports of controversy concerning the claim by Lou Frank of the University of Iowa that he had discovered evidence of mini-comets striking the Earth in quantities approximately the million times greater than would be indicated by other lines of scientific evidence. Although there is almost no support in the scientific community for this mini-comet hypothesis, Frank continues to advocate it, and the press continues to keep the issue alive in the public consciousness. Following are four press releases from the AGU meeting dealing with this issue.

But the snowballs may not exist. University of Washington geophysicist George Parks has analyzed Frank's ultraviolet (UV camera images and has concluded that the white snow in space is no more than black "snow" on the television screen.

 

After a close analysis of one hour of data supplied by Frank, Parks says he and his collaborators are certain that Frank has been looking at "instrument noise." It is very similar, says Parks, "to the static you hear on your hi-fi."

Earth's sky would sparkle like a Christmas tree, its air would hold at least 30,000 times more inert gas and its moon would be pocked with millions more bright-spot craters than spacecraft see if a prominently publicized small-comet theory were correct, scientists from The University of Arizona in Tucson report in the Dec. 15 issue of Geophysical Research Letters.