November 1, 2012

The first analysis of Martian soil by the rover Curiosity has revealed minerals remarkably similar to those found near volcanoes in Hawaii. NASA scientists reported that the soil contained significant amounts of feldspar, pyroxene, and olivine, minerals typically associated with volcanic eruptions on Earth.

The analysis was the first by the rover’s Chemistry and Mineralogy Instrument (CheMin), one of 10 sophisticated scientific instruments aboard Curiosity, the most advanced robotic laboratory ever sent to another planet. Mineral analysis is vital to the rover’s mission, determining whether Mars is, or ever has been, capable of supporting microbial life.

A graph based on an analysis of a soil sample from Mars reveals minerals commonly found in volcanoes in Hawaii. (NASA/JPL-Caltech/Ames)

Curiosity picked up the soil from a site named Rocknest. A sieve in CheMin filtered out all particles larger than 0.006 inch (150 micrometers), about the width of a human hair. The remaining particles were bombarded with X rays to determine their particular internal structure. According to NASA scientists, the minerals are much younger than the water-worn pebbles photographed by Curiosity in September. Those pebbles provided direct evidence that a deep, fast-moving stream of water once flowed across Gale Crater, the rover’s landing site. The soil minerals apparently had only a limited exposure to water and date from a “transition time” when the crater was changing from a wet to a dry environment.

Olympus Mons, a shield volcano, on Mars is the largest volcano in the solar system. (NASA)

Mars has some of the largest volcanoes in the solar system. The highest peak in the solar system is the Martian mountain Olympus Mons (Latin for Mount Olympus). It rises about 16 miles (25 kilometers) above the surrounding plain to a height about three times that of Mount Everest, the highest point on Earth. Olympus Mons, which is more than 370 miles (600 kilometers) in diameter, is a shield volcano, like the volcanoes on Hawaii. Shield volcanoes have slopes that rise gradually. They form from eruptions of lava that can flow for long distances before becoming solid.

Additional World Book articles:

• Hawaii Volcanoes National Park
• Mars Exploration Rover Mission
• Mars Pathfinder
• Phoenix (spacecraft)
• Space exploration (Probes to Mars)
• The Search for Water on Mars (a Special Report)

X-ray diffraction, commonly used on Earth

Determines minerals’ internal structure by recording how their crystals interact with X rays

May 4, 2012

Strange spirals discovered on the surface of Mars strongly suggest that fire, not ice, was responsible for the formation of a region that has puzzled scientists for more than a decade. The spirals–rock formations that look like coils of rope–were discovered by graduate student Andrew Ryan of Arizona State University in images of Athabasca Valles, a network of valleys near the Martian equator. The images were made by a high-resolution camera aboard NASA‘s Mars Reconnaissance Orbiter that can provide clear images of objects about the size of a beach ball at a distance of 185 miles (300 kilometers).

Athabasca Valles is a network of valleys about 185 miles long near the Martian equator. The region’s surface is covered by huge plates that have cracked and broken into thousands of irregularly shaped, multisided blocks. Ryan and his co-author Philip Christensen reported finding 269 spirals, ranging in diameter from 16 to 98 feet (5 to 30 meters), between the blocks.

(NASA/JPL/University of Arizona)

Some scientists have argued that the blocks in Athabasca Valles, which look like Arctic ice floes, formed as sheets of ice moved across the Martian surface. Others argued that the cracks formed because of volcanic activity. Mars has the largest volcanoes in the solar system, including gigantic Olympus Mons. Ryan and Christensen contend that the spirals provide strong evidence for the lava theory. They note that similar features can be seen in the smooth, slow-moving lava flows on Hawaii. There, the rubbery surface of the flows is twisted into coils as the liquid lava streams below move in different directions at different speeds. They argue that a similar process must have produced the spirals in Athabasca Valles. Some scientists, however, continue to argue that ice was responsible for the blocks in the region.

Additional articles in World Book:

• Hawaii Volcanoes National Park
• The Search for Water on Mars (a Special Report)

March 27, 2012

Sometimes things are not as simple as they appear. Take the planet Mercury, for instance. In a very short time, the smallest planet in the solar system (sorry Pluto, you’re no longer a planet) has gone from a simple hunk of rock, much like Earth’s moon, to one of the most unusual planets ever studied. For years, most astronomers thought that Mercury formed early in the solar system’s history and has since remained pretty much unchanged. New evidence shows a planet whose more recent history includes active volcanoes, a shifting crust, and other activities once thought to have ended billions of years ago. Some of these activities may result from the fact that Mercury is slowly shrinking. The shrinking would explain why the outer layer of the planet is buckling and cracking. A closer look at the surface also shows evidence of lava flows having occurred much more recently than previously thought.

The MESSENGER space probe has revealed surprising new findings about the smallest planet in the solar system. (Courtesy of NASA)

The planet’s surface is not the only surprise. Mercury may also have an internal structure like no other planet yet studied by scientists. Mercury appears to have a core consisting of three layers. Earth has only two such inner layers. Both Mercury and Earth have an inner core of solid metal surrounded by a second layer of liquid metal. Unlike Earth, Mercury appears to have a third layer made of solid iron and sulfur. Many scientists now speculate that this possible third layer of core explains one of the great mysteries concerning Mercury. Scientists have long wondered how the planet could be so small and yet have a much greater mass than the other inner planets–Venus, Earth, and Mars–for its size.

The new data on Mercury was collected by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) space probe. Launched in 2004 by NASA, MESSENGER began a one-year mission orbiting Mercury in early 2011 (which NASA scientists have now extended). The probe reached the planet after a more than five-year tour of the inner solar system. The long, looping route involved three close fly-bys of Mercury along with close approaches to Venus and Earth.

Just how loopy was the route MESSENGER took? Mercury is only about 20 percent farther from Earth than Mars when those planets pass closest to Earth. Yet, a probe going to Mars travels for less than a year. By comparison, MESSENGER took more than five years to reach Mercury.

Additional World Book articles

• Probing the Planets (a special report)
• Space Exploration 2004 (Back in Time article)
• Space Exploration 2008 (Back in Time article)
• Space Exploration 2009 (Back in Time article)
• Space Exploration 2011 (Back in Time article)