نتایج جستجو برای: terrestrial atmosphere
تعداد نتایج: 87850 فیلتر نتایج به سال:
O ne of the many changes occurring in the biosphere due . to human activities is the increase in the carbon dioxide concentration of the atmosphere. This change is due both to the burning of fossil fuels, which is ejecting approximately 5-6 gT of carbon into the atmosphere yearly, and to deforestation, which may account for another 1~2 gT (Moore and Bolin 1986/87, Detwiler and Hall 1988). The p...
Using a new measurement of the D/H fractionation efficiency and new estimates of the water loss, we calculate that Mars has the equivalent of a approximately 9 m global water layer in a reservoir that exchanges with the atmosphere. The measured D/H enrichment is about 5 times the terrestrial value, but without exchange, the atmosphere converges on an enrichment of 50 in about 0.5 Ma. Due to the...
We present initial Mars Atmosphere and Volatile EvolutioN (MAVEN) observations and preliminary interpretation of bulk plasma loss from Mars. MAVEN particle and field measurements show that planetary heavy ions derived from the Martian atmosphere can escape in the form of discrete coherent structures or “clouds.” The ions in these clouds are unmagnetized or weakly magnetized, have velocities wel...
Climate catastrophes, which many times occurred in the geological past, caused the extinction of large or small populations of animals and plants. Changes in the terrestrial and marine biota caused by the catastrophic climate changes undoubtedly resulted in considerable fluctuations in global carbon cycle and atmospheric gas composition. Primarily, carbon dioxide and other greenhouse gas conten...
Recently Keppler et al. (2006) discovered a surprising new source of methane – terrestrial plants under aerobic conditions, with an estimated global production of 62– 236 Tg yr−1 by an unknown mechanism. This is ∼10–40% of the annual total of methane entering the modern atmosphere and ∼30–100% of annual methane entering the preindustrial (0 to 1700 AD) atmosphere. Here we test this reported glo...
There have been several reports of exotic nuclear fragments, with highly unusual charge to mass ratio, in cosmic ray experiments. Although there exist experimental uncertainties which make them, at best, only candidate ”exotic” events, it is important to understand what they could be, if they are eventually confirmed. Among other possible explanations, some authors have interpreted them to be l...
Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typi...
Magnetohydrodynamic waves interact with structured plasmas and reveal the internal magnetic and thermal structures therein, thereby having seismological applications in the solar atmosphere. We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one dimensional numerical simu...
The atmosphere of Titan represents a bridge between the early solar nebula and atmospheres like ours. The low abundances of primordial noble gases in Titan's atmosphere relative to N2 suggest that the icy planetesimals that formed the satellite must have originated at temperatures higher than 75-100 K. Under these conditions, N2 would also be very poorly trapped and thus Titan's nitrogen, like ...
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