Category: Venus

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Venus is a world not for the faint of heart. On its surface you’d have to endure high temperatures and intense air pressures, plus within the thick, sulfuric acid-laced atmosphere there are actually lightning storms. These storms are surprisingly similar to lightning storms on Earth, despite the great differences between the atmospheres of the two planets. “Venus and Earth are often called twin planets because of their similar size, mass, and interior structure,” said Dr. Christopher Russell from the University of California, who presented his findings at the European Planetary Science Congress in Rome this week. “The generation of lightning is one more way in which Venus and Earth are fraternal twins.”

Scientists have known there was lightning on Venus since the early planetary missions such as the Venera and Pioneer Venus Orbiter missions, and more recently the Galileo spacecraft reported evidence for optical and electromagnetic waves from Venus that could be produced by lightning. This was also confirmed by ground telescopes capturing lighting flashes at Venus.

Now, the Venus Express spacecraft, in orbit around Venus, has been studying Venus’ lightning in detail with its magnetometer, looking at the rates of discharge, the intensity and the spatial distribution in the magnetic field at altitudes between 200 and 500 km.

Russell said the Venus electromagnetic signals associated with lightning discharges are stronger than terrestrial signals in this frequency band because the background magnetic field is much weaker and the waves travel more slowly, but the electromagnetic energy flux is similar to that on Earth.

“Short strong pulses of the signals expected to be produced by lightning were seen almost immediately upon arrival at Venus, despite the generally unfavorable magnetic field orientation for entry of the signals into the Venus ionosphere at the altitude of the Venus Express measurements,” said Russell.

The observed electromagnetic waves are strongly guided by the Venusian magnetic field and they can only be detected by the spacecraft when the magnetic field tilts away from the horizontal by more than 15 degrees. This is quite unlike the situation on Earth, where the lightning signals are aided in their entry into the ionosphere by the nearly vertical magnetic field.

When clouds form, on Earth or Venus, the energy that the Sun has deposited in the air can be released in a very powerful electrical discharge. As cloud particles collide, they transfer electrical charge from large particles to small, and the large particles fall while the small particles are carried upward. The separation of charges leads to lightning strokes. This process is important for a planetary atmosphere because it raises the temperature and pressure of a small portion of the atmosphere to a very high value so that molecules can form, which would not otherwise occur at standard atmospheric temperatures and pressures. This is why some scientists have speculated that lightning may have helped life to arise on Earth.

“We have analyzed 3.5 Earth-years of Venus lightning data using the low-altitude Venus Express data, which is about 10 minutes per day,” Russell said. “By comparing the electromagnetic waves produced at the two planets, we found stronger magnetic signals on Venus, but when converted to energy flux we found very similar lightening strength,” said Russell. Also it seems that lightning is more prevalent on the dayside than at night, and happens more often at low Venusian latitudes where the solar input to the atmosphere is strongest.”

Source: European Planetary Science Congress

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Venus is so hot, it’s cool! This very groovy 1960’s-looking image shows the temperature distribution within Venus and local mobilization at the surface, and is the result of new model of the atmosphere of Earth’s sister planet. The model reveals that the heat in the atmosphere induced from a strong greenhouse warming might actually have had a cooling effect on Venus’ interior. While counter intuitive, the theory might explain why Venus was a highly volcanic planet in the past. And interestingly, it might mean that Venus may have some active volcanoes even today. If so, that would be like, outta sight, man!

“For some decades we’ve known that the large amount of greenhouse gases in the atmosphere of Venus cause the extreme heat we observe presently,” said Lena Noack from the German Aerospace Center (DLR) in Berlin, lead author of the study who presented her findings at the European Planetary Science Congress (EPSC) in Rome.

“The carbon dioxide and other greenhouse gases that are responsible for the high temperatures were blown into the atmosphere by thousands of volcanoes in the past, “ Noack said. “The permanent heat – today we measure almost 470 degrees Celsius globally on Venus – might even have been much higher in the past and, in a runaway cycle, led to even more volcanism. But at a certain point this process turned on its head – the high temperatures caused a partial mobilization of the Venusians crust, leading to an efficient cooling of the mantle, and the volcanism strongly decreased. This resulted in lower surface temperatures, rather comparable to today’s temperature on Venus, and the mobilization of the surface stopped.”

The source of the magma, or molten rocky material, and the volcanic gases lies deep in the mantle of Venus. The decay of radioactive elements, inherited from the building blocks of the Solar System’s planets, and the heat stored in the interior from planet formation produce enough heat to generate partial melts of silicate-, iron- and magnesium-rich magma in the upper mantle. Molten rock has more volume and is lighter than the surrounding solid rock of identical composition. The magma therefore can rise upwards and eventually penetrate through the rigid crust in volcanic vents, spreading lava over the surface and blowing gases into the atmosphere, mostly greenhouse gases like carbon dioxide (CO2), water vapor (H2O) and sulfur dioxide (SO2).

However, the more greenhouse gases, the hotter the atmosphere – possibly leading to even more volcanism. To find out if this runaway process would end in a red-hot Venus, Lena Noack and Doris Breuer, co-author of the study, calculated for the first time a model where the hot atmosphere is ‘coupled’ to a 3D model of the planet’s interior. Unlike here on Earth, the high temperatures have a much bigger effect at the interface with the rocky surface, heating it up to a large extent.

“Interestingly, due to the rising surface temperatures, the surface is mobilized and the insulating effect of the crust diminishes,” said Noack. “The mantle of Venus loses much of its thermal energy to the outside. It’s a little bit like lifting the lid on the mantle: the interior of Venus suddenly cools very efficiently and the rate of volcanism ceases. Our model shows that after that ‘hot’ era of volcanism, the slow-down of volcanism leads to a strong decrease of the temperatures in the atmosphere”.

The calculations of the geophysicists yield another interesting result: the process of volcanic resurfacing takes place at different places at different times. When the atmosphere cools, the mobilization of the surface stops. However, there are indications from the European Space Agency’s Venus Express mission that there may be a few active volcanoes even today which resurface some spots with lava flows. While no volcanic activity has acutally been seen, Venus Express has detected ‘hot spots’, or unusual high surface temperatures at volcanoes previously thought to be extinct. So far no ‘smoking gun’, or active volcano has been identified on Venus – but it perhaps Venus Express or future space probes will detect the first active volcano on Earth’s neighbor.

Source: European Planetary Science Conference