| |
Records |
Links |
|
Author |
Krasnopolsky, Vladimir A.; Maillard, Jean Pierre; C. Owen, Tobias |
|
| |
Title |
Detection of methane in the martian atmosphere: evidence for life? |
Type |
Journal Article |
| |
Year |
2004 |
Publication |
Icarus |
Abbreviated Journal |
Icarus |
|
| |
Volume |
172 |
Issue |
2 |
Pages |
537-547 |
|
| |
Keywords |
FTS, Mars atmosphere, methane absorption lines, IR spectroscopy, infrared spectroscopy, landfill gas |
|
| |
Abstract |
Using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH4 band at 3.3 μm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centered in the summed spectrum. The observed CH4 mixing ratio is 10±3 ppb. Total photochemical loss of CH4 in the martian atmosphere is equal to View the MathML source, the CH4 lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH4 during its diffusion through the regolith may be significant. There are no processes of CH4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. Outgassing from Mars is weak, the latest volcanism is at least 10 million years old, and thermal emission imaging from the Mars Odyssey orbiter does not reveal any hot spots on Mars. Hydrothermal systems can hardly be warmer than the room temperature at which production of methane is very low in terrestrial waters. Therefore a significant production of hydrothermal and magmatic methane is not very likely on Mars. The calculated average production of CH4 by cometary impacts is 2% of the methane loss. Production of methane by meteorites and interplanetary dust does not exceed 4% of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of “natural gas†on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is a plausible explanation for this discovery. Our estimates of the biomass and its production using the measured CH4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
|
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
no |
|
| |
Call Number  |
|
Serial |
879 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Klapwijk, T. M.; Barends, R.; Gao, J. R.; Hajenius, M.; Baselmans, J. J. A. |
|
| |
Title |
Improved superconducting hot-electron bolometer devices for the THz range |
Type |
Conference Article |
| |
Year |
2004 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
|
| |
Volume |
5498 |
Issue |
|
Pages |
129-139 |
|
| |
Keywords |
HEB mixer distributed model, numerical model |
|
| |
Abstract |
Improved and reproducible heterodyne mixing (noise temperatures of 950 K at 2.5 THz) has been realized with NbN based hot-electron superconducting devices with low contact resistances. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, has been used to understand the physical conditions during the mixing process. We find that the mixing is predominantly due to the exponential rise of the local resistivity as a function of electron temperature. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
|
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
Invited talk, Recommended by Klapwijk |
Approved |
no |
|
| |
Call Number |
|
Serial |
912 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Hubers, H.-W.; Semenov, A.; Richter, H.; Schwarz, M.; Gunther, B.; Smirnov, K.; Gol’tsman, G.; Voronov, B. |
|
| |
Title |
Heterodyne receiver for 3-5 THz with hot-electron bolometer mixer |
Type |
Conference Article |
| |
Year |
2004 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
|
| |
Volume |
5498 |
Issue |
|
Pages |
579-586 |
|
| |
Keywords |
NbN HEB mixers |
|
| |
Abstract |
Heterodyne receivers for applications in astronomy and planetary research need quantum limited sensitivity. In instruments which are currently build for SOFIA and Herschel superconducting hot electron bolometers (HEB) will be used to achieve this goal at frequencies above 1.4 THz. The local oscillator and the mixer are the most critical components for a heterodyne receiver operating at 3-5 THz. The design and performance of an optically pumped THz gas laser optimized for this frequency band will be presented. In order to optimize the performance for this frequency hot electron bolometer mixers with different in-plane dimensions and logarithmic-spiral feed antennas have been investigated. Their noise temperatures and beam patterns were measured. Above 3 THz the best performance was achieved with a superconducting bridge of 2.0 x 0.2 μm2 incorporated in a logarithmic spiral antenna. The DSB noise temperatures were 2700 K, 4700 K and 6400 K at 3.1 THz, 4.3 THz and 5.2 THz, respectively. The results demonstrate that the NbN HEB is very well suited as a mixer for THz heterodyne receivers up to at least 5 THz. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
SPIE |
Place of Publication |
|
Editor |
Zmuidzinas, J.; Holland, W.S.; Withington, S. |
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
|
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
Millimeter and Submillimeter Detectors for Astronomy II |
|
| |
Notes |
|
Approved |
no |
|
| |
Call Number |
|
Serial |
1483 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Meledin, D. V.; Marrone, D. P.; Tong, C.-Y. E.; Gibson, H.; Blundell, R.; Paine, S. N.; Papa, D.C.; Smith, M.; Hunter, T. R.; Battat, J.; Voronov, B.; Gol'tsman, G. |
|
| |
Title |
A 1-THz superconducting hot-electron-bolometer receiver for astronomical observations |
Type |
Journal Article |
| |
Year |
2004 |
Publication |
IEEE Trans. Microwave Theory Techn. |
Abbreviated Journal |
IEEE Trans. Microwave Theory Techn. |
|
| |
Volume |
52 |
Issue |
10 |
Pages |
2338-2343 |
|
| |
Keywords |
NbN HEB mixer, applications |
|
| |
Abstract |
In this paper, we describe a superconducting hot-electron-bolometer mixer receiver developed to operate in atmospheric windows between 800-1300 GHz. The receiver uses a waveguide mixer element made of 3-4-nm-thick NbN film deposited over crystalline quartz. This mixer yields double-sideband receiver noise temperatures of 1000 K at around 1.0 THz, and 1600 K at 1.26 THz, at an IF of 3.0 GHz. The receiver was successfully tested in the laboratory using a gas cell as a spectral line test source. It is now in use on the Smithsonian Astrophysical Observatory terahertz test telescope in northern Chile. |
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
0018-9480 |
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
|
|
| |
Notes |
|
Approved |
no |
|
| |
Call Number |
|
Serial |
1484 |
|
| Permanent link to this record |
| |
|
| |
|
Author |
Slysz, W.; Wegrzecki, M.; Papis, E.; Gol'tsman, G. N.; Verevkin, A.; Sobolewski, R. |
|
| |
Title |
A method of optimization of the NbN superconducting single-photon detector |
Type |
Miscellaneous |
| |
Year |
2004 |
Publication |
INIS |
Abbreviated Journal |
INIS |
|
| |
Volume |
36 |
Issue |
27 |
Pages |
1-2 |
|
| |
Keywords |
NbN SSPD, SNSPD |
|
| |
Abstract |
|
|
| |
Address |
|
|
| |
Corporate Author |
|
Thesis |
|
|
| |
Publisher |
|
Place of Publication |
|
Editor |
|
|
| |
Language |
|
Summary Language |
|
Original Title |
|
|
| |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
|
| |
Series Volume |
|
Series Issue |
|
Edition |
|
|
| |
ISSN |
|
ISBN |
|
Medium |
|
|
| |
Area |
|
Expedition |
|
Conference |
5-th International Symposium Ion Implantation and Other Applications of Ions and Electrons, ION |
|
| |
Notes |
Reference num. 36060124 |
Approved |
no |
|
| |
Call Number |
|
Serial |
1485 |
|
| Permanent link to this record |
