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Walkers winds of Venus, one of the biggest mysteries of the solar system
Walkers winds of Venus, one of the biggest mysteries of the solar system
Because Venus is the closest planet to Earth, it is very convenient for watching. But with all this, “morning star” conceals many mysteries. No, life on it just is not. Scientists are particularly interested in rapidly rotating atmosphere of Venus. This is one of the unsolved mysteries of the solar system, which raises such strong winds in the atmosphere of Venus, that one wind can fly around the planet in four days. Recent satellite data Venus Express has shown that the winds are getting faster.
Being close in size to Earth, Venus is covered by very dense poisonous atmosphere rich in carbon dioxide. The planet’s surface is completely sheltered from soft yellowish veil of clouds. Only ultraviolet wavelength (and to a lesser degree wave infrared) penetrate through the clouds, and then get lost in them because of the unknown ultraviolet absorber in the crush of the clouds. By tracking the movement of the clouds, the observers were able to measure superuragannye winds that circle above the surface of the planet, about 70 km altitude above the scorching lava plains.
Despite decades of observations from the ground and sides of the spacecraft, a number of mysteries remain unsolved. What causes the rotation of the incredible atmosphere of Venus? The winds are moving 50 times faster than the planet itself rotates. As the winds of change as a function of latitude and longitude? How they change over time?
Answers to some of these questions are now trying to get through instruments on board Venus Express, for example, Venus Monitoring Camera (VMC), which oversees the Venusian atmosphere of ten years, the equivalent of six of the earth. VMC makes snapshots of Venus in ultraviolet and near-infrared bands. Simultaneous visualization of the two bands can reveal features of clouds, and thus obtain data about winds at two different levels – 70 and 60 kilometers above the surface.
Venus Express orbit circling to 24 hours, suitable for a distance of approximately 250 km to the north pole, and then moves 66 000 km to the south pole. This elliptical trajectory provides a good environment for monitoring of the entire southern hemisphere, takes pictures in high resolution. These factors, coupled with photos VMC, for the first time allowed a detailed map of the winds, the temperature and the directions for five years.
Recent analyzes of the movement of clouds of Venus and the wind speed, based on data from VMC, made by two independent groups – one of Russia (led by Khatuntseva) and the Japanese team (Kouyama). Carefully measuring the movement of clouds in images VMC, two groups have revealed new patterns in the rotation of the planet.
“We analyzed the images obtained during the orbital flight 127, a manual method of tracking and tracing, and 600 orbits of the method of digital correlation,” – said Igor Khatuntsev of the Space Research Institute in Moscow, in an article in the journal “Icarus”. – “More than 45,000 functions were tracked by the human visual comparison and 350,000 more were observable functions automatically by a computer program.”
Manual method of measuring the wind speed is to track the movement of clouds on several high-contrast images taken at different times. This approach allowed us to make better patterns of movement of clouds and more accurate than those obtained digitally at middle and high latitudes, where the clouds are usually arranged in rows or where low contrast. The only disadvantage of this method – it takes a lot of time.
On the other hand, the technique can track categorize digital image processing and produces 10 times more wind vectors. Both methods are good at low latitudes study (below 40 degrees), but the preferred digital streams in the study at an average speed.
Japanese-Swedish team has relied solely on its automated tracking method, displaying data from multiple images taken with the difference in time, between the latitudes of 55 and 70. The specially developed mathematical formula should reduce the number of errors in the analysis of images. Analysis of this team has been published in the Journal of Geophysical Research.
A detailed analysis revealed an average atmospheric circulation, long-term and daily trends, variations from orbit to orbit and frequency.
In the low latitudes of the middle zone (east-west) wind moves at a speed of about 94 m / s (338 km / h) in a retrograde direction. (The surface of Venus and the atmosphere are moving in a retrograde direction, that is, clockwise from the north pole, in the opposite direction of the other planets). Zonal wind speed reaches a peak at 40-50 degrees S and reaches 102 m / s flows into the middle latitudes. From 50 degrees poleward zonal wind abruptly loses speed. This means that the winds of cloud bypass the planet’s equator in five days, and only three – in the mid-latitudes.
The average meridional wind (from the equator to the pole) slowly increases from zero at the equator to 10 m / s at 50 degrees S At higher latitudes, the meridional wind is gradually slowing to zero speed when approaching the eye of a global fast moving vortex located on the pole.
Perhaps the most important discovery – it is a constant increase in the upper limit of the average wind speed of cloud with 300 km / h to almost 400 km / h in the period from 2006 to 2013.
“This is a huge increase in the already high-speed rotation of the atmosphere”, – said Igor Khatuntsev. – “Such a large spread has never been observed on Venus, and we do not understand why it happened.”
Both papers also showed that the wind speed shows short-term and long-term fluctuations. This includes regular changes associated with the local time of the day and the height of the sun above the horizon.
Other wind speed change is even more difficult to explain. According to some observations, the zonal wind slows down slowly from 100-110 m / s at the equator to less than 50 m / s in the polar region, while other observations wind speed was constant at 40 degrees S with a slight acceleration to 50 degrees.
“We have identified a peak that occurs every 238 days, but it may be a mistake” – says Khatuntsev. – “It can be associated with periods when the VMC could make observations on the dayside of the planet.”
“Our analysis of the daily rate of movement of the clouds, made on the basis of pictures with VMC, showed that the average speed of zonal constantly varies in the range of 20 m / s every 255 days,” – said Toru Kouyama of the Research Institute in Ibaraki in Japan.
“These documents have increased the number of questions that we need to answer and which are associated with atmospheric supervrascheniem Venus. This is one of the greatest unexplained mysteries of the solar system, “- said Hakan Svedhem, project scientist Venus Express. – “Further study of the spatial structure of wind are needed in order to explain what drives atmospheric circulation pattern. Meanwhile, Venus Express continues to amaze us with their observations of this dynamic and changing planet. ”
The first European mission to Venus began with Venus Express launch from Baikonur November 9, 2005 on the launcher “Soyuz-Fregat.” The orbit of Venus unit is out April 11, 2006. Satellite payload includes various spectrometers and spektrofotoapparaty cameras taking pictures in the range from ultraviolet to infrared heat, also on board the analyzer is plasma and magnetometer.
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Tags: Venus , the universe , the solar system .
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