Space probe roundup

There’s a few probes out there, gathering data in the solar system, so starting from the inner planets, today’s news includes:

Venus Express has been watching a vortex playing in the atmosphere above the south pole of Venus. In 1979, the Pioneer Venus mission spotted a vortex above the north pole and on arrival in 2006, Venus Express found its southern twin. However, continuous recording of the phenomenon has shown that the double-eyed appearance of the vortex was simply a coincidence. Other vortices have since come and gone at the south, leaving the double eyed feature nowhere to be found. Full details are here.

Sticking with Venus Express, but delving lower into the atmosphere, lightning discharges on the second planet from the Sun have been confirmed as happening as frequently on Venus – one hundred times a day – as on Earth. The storms are strongest on the dayside, where the Sun provides the energy for cloud particles to collide and rub together, and also strongest towards the equator, for the same reason. The signals, previous detected by other probes using different instrumentation, were detected using Venus Express’s magnetometer and were apparent from the earliest times after insertion into orbit. Full details here.

Onto Earth now and a crater seen in satellite images bundled into the Google Earth software has been confirmed as being an impact feature. The feature was spotted in 2008 in images of the Egyptian desert and has been measured at 45 metres diameter and 16m deep. The crater was forged by the impact of a 1.3m meteorite weighing in at 10 tonnes (one tonne of which has now been collected up) sometime in the last several thousand years. The crater has evaded the geological processes that tend to erode such features and seems to have also escaped notice from human eyes in all that time. More on the discovery and confirmation of Kamil crater (including a google maps page showing the thing) can be seen here.

Three years of data from the SMART-1 mission to look at the Moon have been released by ESA. The three scientific instruments on board the probe were: the Advanced Moon micro-Imager Experiment (AMIE), which was a camera in visible and near infrared light, which watched the terrain changing as the shadows changed and so mapped the southern pole of the Moon to a resolution of 40m per pixel; the SMART-1 InfraRed Spectrometer (SIR), which watched the spectrum of the Moon in the 0.9-2.6 micrometer wavelength range, enabling mapping of pyroxene and olivine in solidified lunar magma exposed by asteroid impacts; the Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS), which mapped the Moon in the 0.5-10keV photon energy range, enabling x-ray reflection spectroscopy of some heavy elements. Fortunately for D-CIXS, a high energy solar flare provided additional x-ray flux enabling some of the elements that would normally be producing very dim signals to shine brightly enough to be confirmed. The data can be found here.

Further out and Mars Express has been used to examine the unusual behaviour of carbon dioxide ice in the Martian polar cap. Observations of the ice showed unusual behaviour as the cap receded in warmer times. The signal of the CO2 is seen to weaken and vanish as it sublimates from ice to gas, but then not long after, the signal suddenly returns before vanishing again. This fade in, it was hypothesised, could be due to a protective layer of dust or water ice protecting the underlying CO2. As there was no change in brightness, as there would be if white ice gave way to dark dust, researchers concluded water ice, invisible to the instruments they were using, must be the insulating layer. The Martian polar caps contain a mixture of water ice and CO2 ice. CO2 sublimates at a lower temperature, so what was happening was the exposed CO2 vanished, leaving a water ice shell (added to by condensing water ice from warmer, lower latitudes) and underlying CO2. Then there came the problem of why the water ice was suddenly stripped away revealing lots of CO2 to provide the second signal. Models of downward flowing winds created by the warming showed that these were capable of doing the stripping, lending the final piece of the theory. Full details here.

The Rosetta probe is set for a date with the Comet 67P/Churyumov-Gerasimenko in May 2014. Computer models of the three dimensional shape and motion of the comet have been used to assess what part of it will be least prone to outgassing as the block of rock and ice closes in on the Sun. The results suggest the southern hemisphere will be the best place for Philae, the lander delivered by the probe, to hook on and sample the comet material. Before the probe meets the comet, this hemisphere will receive the largest amount of sunshine, eroding the outer crust and exposing pristine material within. By the time the probe meets the comet, and after delivery of the lander, the north pole of the comet will be in the glare of the Sun, and so most prone to outbursts. The lander will use harpoons and jets to hook onto the comet during its studies. Full details here.

Cassini will be performing the first in a series of Titan flybys over the next eighteen months later today. The aim will be to supplement climate studies of the distant satellite of Saturn, more details here.

Cassini has also been taking a good look at the parent body in the infrared. Using the Visual and Infrared Mapping Spectrometer, Tom Stallard of Leicester (and formerly UCL) has been observing changes in the southern lights of Saturn to compare with other processes going on in Saturn’s magnetosphere, the aim being to connect the two. The aurora of Saturn are complex and involve both large scale motions of the magnetosphere – contractions and expansions caused by the uneven passage of the pulsed solar wind – and small scale structure such as disruption of particle and energy flows by the moons of Saturn inside the magnetosphere. More details of his infrared work are here and some images of ultraviolet auroral signals from Saturn and Jupiter by the Hubble Space Telescope are here.


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