* Astronomy

Members Login
Post Info TOPIC: Cosmic Dust Centre


L

Posts: 131433
Date:
RE: Cosmic Dust Centre
Permalink  
 


Title: An Antarctic ice core recording both supernovae and solar cycles
Authors: Yuko Motizuki, Kazuya Takahashi, Kazuo Makishima, Aya Bamba, Yoichi Nakai, Yasushige Yano, Makoto Igarashi, Hideaki Motoyama, Kokichi Kamiyama, Keisuke Suzuki, Takashi Imamura

Ice cores are known to be rich in information regarding past climates, and the possibility that they record astronomical phenomena has also been discussed. Rood et al. were the first to suggest, in 1979, that nitrate ion (NO3-) concentration spikes observed in the depth profile of a South Pole ice core might correlate with the known historical supernovae (SNe), Tycho (AD 1572), Kepler (AD 1604), and SN 1181 (AD 1181). Their findings, however, were not supported by subsequent examinations by different groups using different ice cores, and the results have remained controversial and confusing. Here we present a precision analysis of an ice core drilled in 2001 at Dome Fuji station in Antarctica. It revealed highly significant three NO3- spikes dating from the 10th to the 11th century. Two of them are coincident with SN 1006 (AD 1006) and the Crab Nebula SN (AD 1054), within the uncertainty of our absolute dating based on known volcanic signals. Moreover, by applying time-series analyses to the measured NO3- concentration variations, we discovered very clear evidence of an 11-year periodicity that can be explained by solar modulation. This is one of the first times that a distinct 11-year solar cycle has been observed for a period before the landmark studies of sunspots by Galileo Galilei with his telescope. These findings have significant consequences for the dating of ice cores and galactic SN and solar activity histories.

Read more (342kb, PDF)

__________________


L

Posts: 131433
Date:
Cosmic dust particles
Permalink  
 


The origin of the microscopic meteorites that make up cosmic dust has been revealed for the first time in new research out today (1 September 2008).
The research, published in the journal Geology, shows that some of the cosmic dust falling to Earth comes from an ancient asteroid belt between Jupiter and Mars. This research improves our knowledge of the solar system, and could provide a new and inexpensive method for understanding space.
Cosmic dust particles, originally from asteroids and comets, are minute pieces of pulverised rock. They measure up to a tenth of a millimetre in size and shroud the solar system in a thin cloud. Studying them is important because their mineral content records the conditions under which asteroids and comets were formed over four and a half billion years ago and provides an insight into the earliest history of our solar system.

Read more


__________________


L

Posts: 131433
Date:
Cosmic Dust
Permalink  
 


The idea that cosmic dust triggers glaciation on Earth has been blown away.

It was previously thought that an excess of cosmic dust falling on Earth could encourage clouds to form, causing more sunlight to reflect back into space and tipping Earth into a glacial cycle.
Gisela Winckler from the Lamont-Doherty Earth Observatory in New York and her colleague have found that this is not the case. They measured levels of helium-3 (an isotope that is rare on Earth but abundant in space) in an Antarctic ice core going back nearly 30,000 years, and showed that levels of cosmic dust falling on Earth have been relatively steady and could not have affected the glacial cycles (Science, vol 313, p 491).

Source

Read more

__________________


L

Posts: 131433
Date:
Dust in Antarctic Ice
Permalink  
 


Each year nearly 40,000 tons of cosmic dust fall to Earth from outer space. Now, the first successful chronological study of extraterrestrial dust in Antarctic ice has shown that this amount has remained largely constant over the past 30,000 years, a finding that could help refine efforts to understand the timing and effects of changes in the Earth's past climate.

The same study also used an improved analytical technique to show that dust carried to Antarctica from continental sources changed depending on climate.
The study, which appears in the July 28 issue of the journal Science, involved researchers from the Lamont-Doherty Earth Observatory, a part of The Earth Institute, and the Alfred Wegener Institute for Polar and Marine Research (AWI) in Bremerhaven, Germany. The depth of the core they examined corresponded to the period between 6,800 and 29,000 years before the present day — a span that includes the height of the last glacial period, and the transition to warm conditions similar to today.
The scientists collected particulate matter from the EPICA (European Project for Ice Coring in Antarctica) ice core and measured the concentration of helium-3 (3He), a rare isotope that is plentiful in the sun's solar wind and is carried to Earth imbedded in cosmic dust particles measuring just a few thousandths of a millimetre in diameter. These dust particles carry their exotic helium load to the Earth’s surface where they are preserved in the snow and ice of the polar ice caps, among other places.
Because ice cores from the polar caps provide a high-resolution temporal record of the past, the researchers were able to measure fine variations in the rate of cosmic dust accumulation between glacial and interglacial periods as well as the helium isotope characteristics of these rare particles. They found that the accumulation of cosmic dust did not change appreciably as the Earth emerged from the last great Ice Age and entered the current warm period, a fact that is likely to bolster the use of cosmic dust measuring techniques in future climate studies.
In addition, this was the first study to examine both cosmic and terrestrial dust using the same helium-isotope technique. As a result, they also found that the composition of mineral dust particles carried by wind from the southern continents to Antarctica changed considerably as the Earth's climate changed.

"The terrestrial dust coming down on Antarctica during the Ice Age obviously is not the same as that during warm periods. This may be due to the mineral dust originating from different regional sources or to changes in the process responsible for producing the dust" - Gisela Winckler, a Doherty associate research scientist at Lamont-Doherty and lead author on the study.

The project was supported by the Comer Science and Education Foundation.

Source

__________________


L

Posts: 131433
Date:
RE: Cosmic Dust
Permalink  
 


For the last 30,000 years, our planet has been hit by a constant rain of cosmic dust particles. Two scientists from the Lamont-Doherty Earth Observatory (LDEO) at Columbia University in New York and the Alfred-Wegener-Institut (AWI) for Polar and Marine Research in Bremerhaven, Germany, have reached this conclusion after investigating the amount of the helium isotope 3He in cosmic dust particles preserved in an Antarctic ice core over the last 30,000 years. They have shown that this rare helium isotope in cosmic dust exceeds that of terrestrial dust in ice by a factor of 5,000. Moreover, measurements of the amount of 4He – a helium isotope much more common on Earth – in the Antarctic ice strongly suggest a change of origins in terrestrial dust between the last Ice Age and the interglacial warm period we currently live in.

Read more

__________________


L

Posts: 131433
Date:
Cosmic Dust Centre
Permalink  
 


A $1.5 million grant gives UH researchers the tools to analyze bits of cosmic dust

The University of Hawaii is developing one of the world's most advanced laboratories to study the origin of the solar system.
"The university is trying to build the premier centre in the world for studies of primitive materials, cosmic dust, meteorites and samples from other planets" - Peter Mouginis-Mark, acting director of the Hawaii Institute of Geophysics and Planetology.



The UH Foundation received $1.5 million from the W.M. Keck Foundation to create the new lab, which uses an array of sciences called cosmochemistry to analyze bits of meteorites, planets and comet dust. UH matched it with $1 million, and NASA approved $1.4 million to acquire a state-of-the-art ion microprobe for the laboratory, Mouginis-Mark said.
The instrument is being built in France. "It's huge. I'm not even sure how we're going to get it into the (Pacific Ocean Science and Technology ) building, but we'll find a way."
Klaus Keil, interim dean of the School of Ocean Earth Sciences and Technology, said the UH research group will "really make a quantum leap forward in the field of cosmochemistry."
Joining the group are two world experts in ion microprobe analysis and cosmochemistry: Gary Huss, formerly of the University of Arizona, and Kazu Nagashima, formerly of the Tokyo Institute of Technology.
"What we're going to do is look at samples from the earliest solar system, which are mostly meteorites but will include comet dust from the Stardust Mission to the comet, and samples from the moon and potentially samples from Mars, and we will investigate how they formed"
Meteorites and comets probably date from the earliest times of the solar system, "so when we look at those, we see the very earliest building blocks of the solar system, and we have the ability to investigate processes that occurred in the early solar system" - Gary Huss.
The main advantage of the ion probe is they can measure samples without having to dissolve or destroy them, "We can measure spots on polished samples only a few microns across… We investigate the materials, processes and timing of events in the early solar system to try to piece together the story of how the solar system formed."
The raw materials for the early solar system are "surviving grains that formed around other stars at the end of their lives. The elements heavier than hydrogen and helium were produced by nuclear processes in stars, and they are dispersed through the galaxy when a star either ejects its envelope or explodes at the end of its life."
The scientists can investigate the timing of events in the early solar system with the ion probe.
"We now know that the formation of bodies the size of the current asteroids took only a few million years after the solar system began and that the earth formed shortly thereafter."
UH-Manoa Chancellor Peter Englert said the Keck Foundation award "highlights both the quality and range of research expertise at the university and is a testament to our growing reputation within the international scientific community."
The Institute of Geophysics and Planetology has a renowned group of scientists studying meteorites and data from Mars and other planets.
Their program has been involved with present and planned spacecraft missions that will return samples, such as Genesis, Stardust and Mars sample return programs.
The program also provides critical information for interpretation of remote sensing data and addresses questions posed by materials obtained from deep interiors of stars or planets.


source


__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard