Far Side of The Moon

The Far Side of The Moon



Credit: JAXA
Gravity






Credit: JAXA
Topography


Figures: The topography maps and free-air gravity maps of the global Moon obtained by JAXA's KAGUYA spacecraft. The far-side is on the left and the near-side is on the right.


"Previous models of far-side gravity of the Moon were not accurate, since from the Earth we cannot track directly the spacecraft over the far-side. KAGUYA has a subsatellite OKINA which can relay the radiowave between the ground and the main satellite, thus establishing a link between the ground station and the main satellite while it is over the far side of the Moon. The orbital tracking of KAGUYA using OKINA produced the first accurate lunar gravity map including the far-side. The lunar far-side impact structures show a lack of strongly extended density anomalies which are observed beneath some impact basins in the near-side. The result suggests that far-side crust was cooler and harder than that of the nearside."

Venus Rotation

Complex Rotation on Venus



Credit: UPV/EHU



Venus Express



Credits: ESA (Image by AOES Medialab)

The Basques have taken data from the Venus Express and discovered some surprising news about the complex rotation patterns of Venus: Please note that this is planetary geodesy; learning about the shape, velocity fields, rotation and gravity of planets...Just had to tell you. :-)

Geodesy is the science of determining the geometry, gravity field, and rotation of the Earth and their evolution in time.

Planetary geodesy is geodesy applied on other planets.

Venus

Windy Venus and Rotation




Venus, Mars and Earth, three out of the four inner or ‘rocky’ planets of the Solar System, have a lot in common yet very different.

Their masses are basically the same, and their densities too. Their radii seem just copied from one planet to the other. Their distances from the Sun are not so different – Venus is about 108 million kilometres and Earth is 150 million kilometres.

Their rocks are both largely basaltic, result of intense volcanism and of a similar solidification process, initiated about at the same time, four and a half thousand million years ago, when the planets of the Solar System started to form from the solar ‘proto-planetary nebula’

Rotation
Venus rotates backwards with respect to Earth, so the Sun appears rising from west. It also rotates very slowly – one rotation, or sidereal day, takes 243 Earth days. This is longer than the Venusian year, 225 Earth days long. However its winds are so fast that they can circumnavigate the planet in only four Earth days.

Venus' dense atmosphere of carbon dioxide with surface pressures 90 times that of Earth (equivalent to what we find at 1000 metres below the surface of our oceans), causes a runaway greenhouse effect that raises the surface temperatures up to 450ºC, to such as extent that metals like lead are in a liquid state on Venus. At a height of between 45 km and 70 km above the surface there are dense layers of sulphuric acid clouds totally covering the planet.

In the 1960s it was discovered that the top level of cloud layers moved very rapidly, orbiting the planet in only four days, compared to the planet’s own orbit of 224 days. This phenomenon was baptised the “superotation” of Venus: the winds carrying these clouds travel at 360 km/h.

Hurricane winds and huge atmospheric vortexes are being studied closely based on new data from Venus Express.




Scientists from University of the Basque Country have discovered novel aspects of Venusian rotation.

By using images recorded by both day and night on Venus with the VIRTIS spectral camera on board the Venus Express, scientists have succeeded in measuring these clouds over several months and have discovered new aspects of the “superotation”. Firstly, between the equator and the median latitudes of the planet there dominates a superotation with constant winds blowing from East to West, within the clouds decreasing speed with height from 370 km/h to 180 km/h. At these median latitudes, the winds decrease to a standstill at the pole, where an immense vortex forms. Other aspects of the superrotation that observations with VIRTIS have made possible are that the meridional (North – South) movements are very weak, about 15 km/h, and, secondly, unlike what was previously believed, the superotation appears to be not so constant over time: “We have detected fluctuations in its speed that we do not yet understand”, stated the scientists. Moreover, for the first time they observed “the solar thermal tide” effect at high latitudes on Venus. “The relative movement of the Sun on the clouds and the intense heat deposited on them makes the superotation more intense at sunset than at sunrise”, they stated.

“Despite all the data brought together, we are still not able to explain why a planet than spins so slowly has hurricane global winds that are much more intense than terrestrial ones and are, moreover, concentrated at the top of its clouds” stated Mr Sánchez Lavega. This study has enabled advances to be made in a precise explanation of the origin of superotation in Venusian winds as well as in the knowledge of the general circulation of planetary atmospheres.



Credits: ESA (Image by AOES Medialab)
Venus Express is studying largely unknown phenomena in the Venusian atmosphere like never before. Its suite of instruments is also digging into the interaction between the solar wind and the planetary environment. In addition, the mission is gathering glimpses of the planet's surface, which is strictly coupled with its dense atmosphere.



Credits: ESA/MPS/DLR/IDA

This beautiful, false-colour ultraviolet image of the Southern hemisphere of Venus was obtained by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express on 27 July 2007. It was taken from a distance of 30 000 km from the planet’s surface at a wavelength of 365 nanometres. The planet is seen from the southern hemisphere: the south pole is at the bottom, while equator is at the top.

The shape of the clouds changes dramatically from the equator to the pole. At low latitudes, the cloud shape is spotty and fragmented, a consequence of a vigorous convective movement powered by the radiation of the sun heating the atmosphere itself. The bright lace visible on top of the darker cloud deck is made of freshly formed droplets of sulphuric acid.

At mid latitudes, the convective clouds make way for more streaky shapes indicating that the flow is basically laminar in this portion of the atmosphere.

At high latitudes, the cloud structure appears as a dense, almost featureless haze forming some a ‘polar cap’ on Venus. The dark, circular feature visible at the rightmost edge of the image is one of the dark streaks usually present in the polar region, indicating atmospheric parcels spiralling towards the pole.







Sources: Measuring Wind on Venus and ESA's Venus Express

Mapping Planets

Planetary Cartography



Robert Gaskell is currently working on turning the images of Mercury sent back by the MESSENGER probe into a topographical map. Image: NASA/JHUAPL/Carnegie Institution of Washington.




A NASA image of asteroid Eros (left) and Robert Gaskell's shape model of the asteroid (right). Credit: NASA/JPL/PSI/Robert Gaskell

Mapping Planets

Mapping Exoplanets



Credit: NASA/JPL-Caltech/T. Pyle (SSC)

Wonder how you map so distant bodies? Click on images above and get a how-to video or two. :-)





This is the first-ever map of the surface of an exoplanet, or a planet beyond our solar system. The map, which shows temperature variations across the cloudy tops of a gas giant called HD 189733b, is made up of infrared data taken by NASA's Spitzer Space Telescope. Hotter temperatures are represented in brighter colors.

Wandering Poles

Polar Wandering on Europa




Credit: Paul Schenk

Europa is a complex and dynamic moon, but now, global mapping of unusual large circular features on the ice-covered ocean world of Europa has revealed that Jupiter's curious icy moon is even more unstable than previously thought.



Because of the strong pull of Jupiter's gravity, Europa's icy shell bulges slightly at the equator and is flattened at the poles. The shell is also thought to be separated from Europa's core by an ocean, which would permit the shell to move en masse -- a phenomenon called true polar wander.

Europa is not the only planet or moon to have undergone polar wander. Mars has probably tilted over at least once, due to the formation of the Tharsis volcanos. Earth's outer layers have done so, as apparently have Enceladus, and possibly Miranda. Polar wander may be a common occurrence across the solar system, suggesting that planets in general are less stable than we have thought.

I think we might have to install a GPS network on Europa as well, to sort this out! :-)