Dust devils on Mars

Large columns of dust have been discovered rising above plains on Mars. The storms are probably analogous to terrestrial dust devils, but their size indicates that they are more similar to tornadoes in intensity. They occur at locations where the soil has been strongly warmed by the Sun, and there the surface is smooth and fine grained. These are the same conditions that favor dust devils on Earth. Warm gas from the lowest atmospheric layer converges and rises in a thin column, with intense swirl developing at the edge of the column. In one area a mosaic of Viking images shows 97 vortices in a three day period. This represents a density of vortices of about one in each 900 square kilometers. Thus, these dust devils may be important in moving dust or starting over dust storms

Mesoscale waves as a probe of Jupiter's deep atmosphere

Images from the Voyager north/south mapping sequences were searched for waves. A remarkable class of mesoscale waves was identified, with the following features: (1) the wavetrains are usually aligned zonally, i.e., wavecrests are north-south; (2) the average wavelength is 300 km with a standard deviation of only 20%; (3) the wavetrains are long; (4) the waves occur within 25 degrees of the equator, the bulk being at the equator itself; (5) the waves are centered at the extrema (in latitude) of the zonal flow; and (6) the meridional extent of the waves is typically 1 degree of latitude. These observations are interpreted as evidence of gravity waves propagating vertically within a leaky duct. A three-level model is assumed composed of a stable duct which extends up to the base of the NH3 cloud deck near 600 mb. Above this is a thin wave-trapping region characterized by a Richardson number Ri less than 1/4 and containing a critical level, where the local value of the zonal flow velocity equals the phase speed of the wave. This in turn is overlain by a stable region, representing the tropopause region and stratosphere

Polar sediment accumulation: Role of surface winds at the two poles

The accumulation of the large deposits of volatile and nonvolatile sediments at both Martian poles has occurred through periods of likely climate change. Most data on wind directions near the Martian poles and seasonal activity relate to a very short period of time, at one point in climate cycles. It is still uncertain what the net budgets to the poles are and how this budget (if known) would fit into longer climate/sediment cycles. Pending further data we examined the full suite of Viking high-resolution, high-latitude images for wind markers of all sizes and types. These probably represent timescales of formation from days to several tens of thousands of years. The goal is to estimate the effectiveness, and possible drivers, of wind systems that bring materials near the surface to the regions of polar sediments and that also remove materials from the polar areas

The global energy balance of Titan

The global energy budget of planets and their moons is a critical factor to influence the climate change on these objects. Here we report the first measurement of the global emitted power of Titan. Long-term (2004–2010) observations conducted by the Composite Infrared Spectrometer (CIRS) onboard Cassini reveal that the total emitted power by Titan is (2.84 ± 0.01) × 10^(14) watts. Together with previous measurements of the global absorbed solar power of Titan, the CIRS measurements indicate that the global energy budget of Titan is in equilibrium within measurement error. The uncertainty in the absorbed solar energy places an upper limit on the energy imbalance of 6.0%

Dynamics of Jupiter’s atmosphere

Giant planet atmospheres provided many of the surprises and remarkable discoveries of planetary exploration during the past few decades. Studying Jupiter's atmosphere and comparing it with Earth's gives us critical insight and a broad understanding of how atmospheres work that could not be obtained by studying Earth alone

An interdomain sector mediating allostery in Hsp70 molecular chaperones

The Hsp70 family of molecular chaperones provides a well defined and experimentally powerful model system for understanding allosteric coupling between different protein domains.New extensions to the statistical coupling analysis (SCA) method permit identification of a group of co-evolving amino-acid positions—a sector—in the Hsp70 that is associated with allosteric function.Literature-based and new experimental studies support the notion that the protein sector identified through SCA underlies the allosteric mechanism of Hsp70.This work extends the concept of protein sectors by showing that two non-homologous protein domains can share a single sector when the underlying biological function is defined by the coupled activity of the two domains

Equatorial winds on Saturn and the stratospheric oscillation

The zonal jets on the giant planets have been thought to be stable in time. A decline in the velocity of Saturn’s equatorial jet has been identified, on the basis of a comparison of cloud-tracking data across two decades, but the differences in cloud speeds have since been suggested to stem from changes in cloud altitude in combination with vertical wind shear, rather than from temporal changes in wind strength at a given height. Here, we combine observations of cloud tracks and of atmospheric temperatures taken by two instruments on the Cassini spacecraft to reveal a significant temporal variation in the strength of the high-altitude equatorial jet on Saturn. Specifically, we find that wind speeds at atmospheric pressure levels of 60 mbar, corresponding to Saturn’s tropopause, increased by about 20 m s^(−1) between 2004 and 2008, whereas the wind speed has been essentially constant over time in the southern equatorial troposphere. The observations further reveal that the equatorial jet intensified by about 60 m s^(−1) between 2005 and 2008 in the stratosphere, that is, at pressure levels of 1–5 mbar. Because the wind acceleration is weaker near the tropopause than higher up, in the stratosphere, we conclude that the semi-annual equatorial oscillation of Saturn’s middle atmosphere is also damped as it propagates downwards