The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We present observational data for two long-period and three dynamically new comets observed at heliocentric distances between 5.8 to 14.0 AU. All of the comets exhibited activity beyond the distance at which water ice sublimation can be significant. We have conducted experiments on gas-laden amorphous ice samples and show that considerable gas emission occurs when the ice is heated below the temperature...
From recent close encounters with Comets Wild-2 and Tempel 1 we learned that their surfaces are very rugged and no simple uniform layers model can be applied to them. Rather, a glaciological approach should be applied for describing their surface features and behavior. Such intrinsically rugged surface is formed in our large scale experiments, where an agglomerate of ∼200 μm gas-laden amorphous ice...
Recent attempts using high resolution spectra to detect N +2 in several comets were unsuccessful [Cochran, A.L., Cochran, W.D., Baker, E.S., 2000. Icarus 146, 583–593; Cochran, A.L., 2002. Astrophys. J. 576, L165–L168]. The upper limits on N +2 in comparison with the positively detected CO + for Comets C/1995 O1 Hale–Bopp, 122P/1995 S1 de Vico and 153P/2002 C1 Ikeya–Zhang...
Following the observations of ice grains in cometary comae and their size distributions, we reexamined experimentally our previous conclusion that the ice grains which agglomerated to form comet nuclei were formed at ∼25 K. The suggestion of a ∼25 K formation temperature was confirmed experimentally. Moreover, we suggest that these ice grains had to be of submicron size.
The effect of water ice formation temperature and rate of ice deposition on a cold plate on the amount of trapped argon (equivalent to CO), and the ratios of Ar/Kr/Xe trapped in the water ice were studied at 50, 27 and 22 K and at ice formation rates ranging over four orders of magnitude, from 10 -1 to 10 -5 μm min -1 . Contrary to our previous conclusions that...
Gas trapping by clathrate-hydrate formation in low temperature ''cometary'' water ice has been quoted repeatedly, especially regarding CO. However, of the plethora of gases detected in Comets Halley, Hyakutake, and Hale-Bopp, only methanol (CH 3 OH) and hydrogen sulfide (H 2 S) were shown experimentally to form clathrate-hydrates under the low temperatures and densities of the solar...
The isotopic enrichment in argon, krypton, and xenon, when trapped in water ice, was studied experimentally. The isotopes were found to be enriched according to their (m 1 /m 2 ) 1/2 ratio. These enrichment factors could be useful for comparison among the uncertain cosmic or solar isotopic ratios, the hopeful in situ cometary ratio, and those in Earth's atmosphere,...
The isotopic enrichment of HDO over H 2 O when water vapor freezes into ice at 60–170 K was studied experimentally. No such enrichment was detected (1.003–1.007 in the 95% confidence interval). Thus HDO cannot be enriched when ice is formed by freezing of water vapor. The very similar D/H ratio in the water of Comets Halley, Hyakutake, and Hale–Bopp (∼3 × 10 −4 ) is 10–20 times larger...
HCN andn-C 6 H 14 were found experimentally to be trapped in water ice, when codeposited with water vapor on a cold plate, at 140 K and CH 3 OH even at 160 K. At these temperatures at least part of the water ice is cystalline. These three gases have relatively high sublimation temperatures, whereas the gases studied earlier, Ar, Kr, Xe, CO, CH 4 , and N 2 ...
It is demonstrated experimentally that the CO/H 2 O, CH 4 /H 2 O, and C 2 H 6 /H 2 O ratios found by Mummaet al.(1996) in Comet Hyakutake could be obtained by the trapping of these gases in water ice which was formed at 64–66 K. The formation of the ice particles which formed comets, either in the warm outskirts of the interstellar cloud or in the outer...
Observations of Comet P/Halley showed a cosmic abundance ratio of carbon and oxygen but a depletion of nitrogen. We checked the composition of amorphous water ice samples deposited on a cold plate from gaseous mixtures with various CO:N 2 :H 2 O-vapor ratios at several temperatures. From measuring the amounts of N 2 and CO which are trappedtogetherin the ice, we found an obvious...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.