On Mars' desolate landscape is a giant 50 mile (75km) crater, known as Ismenia Patera, that has left astronomers baffled.Measuring 18x25 miles (40x30km) at its deepest point, the crater dips as low as 5,700 feet (1750m) below the surrounding plains.Nobody knows how this part of Mars 'exploded', but they have some theories.One explanation is that Ismenia Patera was left behind by a meteorite impact, while another claims that the hole is the site of a supervolcano that collapsed in on itself.Now, new images of the area by the European Space Agency have revealed the crater in unprecedented detail - and they could finally help reveal what caused it to form.Crater-like features which could be the footprints of the cataclysmic events have been discovered at several sites in the Martian northern highlands over the past few years.One theory is that the crater was caused by meteorite that collided with Mars.Sedimentary deposits and ice could have flowed in to fill the crater until it collapsed to form the fissured, uneven landscape seen today.However, impact craters normally include features such as a central peak and uplifted crater rims that are not present at the Ismenia Patera.Scientists believe an alternative is that it formed from massive volcanic explosions that blasted ash and lava out of the planet's surface more than three billion years ago.'On Mars, young volcanoes have a very distinctive appearance that allows us to identify them,' said Joseph Michalski, a researcher affiliated with the Planetary Science Institute and the Natural History Museum in London who was researching the site back in 2013.'The long-standing question has been what ancient volcanoes on Mars look like. Perhaps they look like this one', he said.Supervolcanoes occur when magma is trapped below the surface, leading to a huge built up in pressure.They erupt suddenly in violent explosions and so do not 'grow' sloping mountains like Olympus Mons.This makes them hard to identify, especially millions or billions of years later, according to the European Space Agency.On Earth, a supervolcano is defined as a volcano that can produce at least 1,000 cubic kilometres of volcanic materials in an eruption – thousands of times larger than 'normal' volcanic eruptions and powerful enough to alter global climate.An example is the Yellowstone caldera in the United States.'This highly explosive type of eruption is a game-changer, spewing many times more ash and other material than typical, younger Martian volcanoes,' said Jacob Bleacher of NASA's Goddard Space Flight Center, who was researching the site in 2015.'During these types of eruptions on Earth, the debris may spread so far through the atmosphere and remain so long that it alters the global temperature for years.'The two depressions either side of the Ismenia Patera crater could even represent two different eruptive episodes due to collapse as the underlying magma pressure was released, or as the magma chamber migrated below the surfac
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