Moon and Mars

Some of the most imposing features on Mars are its giant volcanoes. The largest is Olympus Mons. It’s more than 13 miles high, and covers an area as big as New Mexico. It’s part of the largest complex of volcanoes on the planet – a region called Tharsis Ridge. The second-largest group is on Elysium Rise. Its largest member is Elysium Mons. It’s the fourth-highest mountain on the planet. It has an elevation of about 10 miles above the Martian equivalent of “sea level,” and it towers about eight miles above the surrounding plains. Like the other major volcanoes, it’s extinct – or at least dormant. It probably hasn’t erupted in hundreds of millions of years. It formed over billions of years, from layers of lava and ash. It’s marred by many craters. Some of them are impact craters, carved by giant space rocks. Others may be volcanic vents, formed by side eruptions of gas or lava. The volcanoes on Mars have grown so big mainly because there are no plate tectonics. Once a pool of magma forces its way to the surface, it just keeps going – the crust above it doesn’t move away. So there’s no “cut-off” valve – the volcano erupts as long as there’s molten rock below to keep feeding it – building some giant mountains on the Red Planet. Mars appears below the Moon in tomorrow’s early morning sky. It looks like a fairly bright orange star. More about the Moon and its companions tomorrow. Script by Damond Benningfield