December 9, 2014

Data from NASA’s Curiosity rover have revealed fascinating new details about the ancient geology of Mars, including the formation of Mount Sharp (also known as Aeolis Mons) and the abundance of surface water. The findings have also increased the likelihood that Earth may not have been the only planet in the solar system with primitive life billions of years ago.

Curiosity scientists reported that they think they have discovered why a 3-mile- (5-kilometer-) high mountain sits in the middle of Gale Crater, the impact crater where the rover landed in August 2012. Before Curiosity, scientists knew that Mount Sharp, like some mountains on Earth, consists of layer upon layer of sediment (layers of dirt, stone, and other materials laid down over many millions of years. But they did not know how Mount Sharp formed because, unlike Earth, Mars has not been shaped by plate tectonics. One theory was that the mountain formed from material that was thrown up as an asteroid or meteor crashed onto the surface there about 3.5 billion years ago. Another theory suggested that the mountain was “excavated” as sediments were eroded from around the peak. Studies made as Curiosity treks up the mountain now suggest that both wind and water were likely involved in the process.

Patterns of sedimentary deposits in Gale Crater suggests the crater held a lake more than 3 billion years ago, filling and drying in cycles that lasted tens of millions of years. (NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS)

Curiosity scientists think that Gale Crater experienced repeated wet and dry episodes that lasted for millions, or tens of millions, of years. During the wet episodes, rivers carrying water filled with sand and rock flowed over the crater’s rim to the floor, forming one large lake or even several smaller lakes. Over time, the sediments settled out of the water and hardened into layers that may have completely or partially filled the crater. During the dry episodes–when the water in the lakes evaporated–Martian winds sculpted the mountain by blowing away some of the sediment around the rim. Gradually, the mound in the center of the crater grew higher and higher.

Mount Sharp in Gale Crater likely formed from layers of sediment (yellow) carried by wind and by rivers flowing over the crater’s rim (above). The sediments then settled out in the center of the crater, forming rock (brown). Wind then eroded the sedimentary rock around the rim, forming Mount Shap. (NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS)

The existence of surface water–as well as underground water–on Mars for such a long period–perhaps 1 billion years–increases the chances that primitive life may have developed on the planet billions of years ago. In such a stable environment, which could have lasted for some 1 billion years, life could have arisen on the red planet some 3.8 billion years ago, as it did on Earth.

Additional World Book articles:

• Mars Pathfinder
• Phoenix [spacecraft]
• Space exploration (Probes to Mars)
• The Search for Water on Mars (a Special Report)

January 27, 2014

Opportunity, the hardy Mars rover that was expected to operate for just 90 days, has marked its 10th anniversary on the red planet. Even more amazingly, the rover, part of the Mars Exploration Rover Mission, is still revealing new information about Mars. NASA launched Opportunity and its twin, Spirit, in 2003 to study the history of water on the red planet. Their  90-day mission, which began in 2004, turned out to be merely a warm-up. Both rovers continued to gather information without any major setbacks for more than five years.

While traversing Mars, the rovers found evidence of ancient hot springs and thermal vents, the first meteorite ever discovered on another world, and rocky spheres created from water-bearing minerals. With Spirit, Opportunity also took the first photos of Earth-like clouds in the Martian sky from the planet’s surface. In early 2009, Spirit became permanently trapped in a bed of loose soil. NASA ended that rover’s mission in 2011. But Opportunity rolled on. The rover has now clocked up about 24 miles (38.7 kilometers) and taken 170,000 photographs.

Opportunity on Mars, in an artist's illustration. (Courtesy NASA/JPL-Caltech)

The rover’s latest discoveries involve rocks dated to about 4 million years ago, the oldest ever discovered by the rover. Opportunity’s analysis of the rocks has provided more evidence for than the surface of Mars was once  warmer and wetter than scientists had thought. Moreover, the rocks formed in water that was less acidic—and thus, more hospitable to microbial life—than the rocks analyzed previously by the rover.

Additional World Book articles:

• Mars Pathfinder
• Mars Science Laboratory
• Space exploration
• The Search for Water on Mars (a special report)

October 4, 2013

Hopes that microbes may be living beneath the harsh surface of Mars have been seriously dampened by new findings from the Curiosity rover. Over the past 10 years, Mars-orbiting satellites and telescopes on Earth have produced data showing small but significant amounts of methane gas in the red planet’s atmosphere. Although methane can be produced by geological processes, most of the methane in Earth’s atmosphere is a by-product of animal digestion or comes from decaying plants. Perhaps, scientists thought, the same was true on Mars. However, a study by Curiosity failed to detect any methane at all, scientists at NASA’s Jet Propulsion Laboratory reported.

From October 2012 to June 2013, Curiosity searched for signs of methane in samples of the Martian atmosphere using its Sample Analysis at Mars (SAM) laboratory. The previous research had revealed methane levels of up to 45 parts per billion (ppb). But Curiosity’s data showed nothing above 1.3 ppb, the minimum detectable by the SAM laboratory. Curiosity’s findings suggest that the satellite and telescope readings were incorrect or that the gas has disappeared. But Sushil Atreya of the University of Michigan, Ann Arbor, one of the paper’s co-authors, said, “There’s no known way for methane to disappear quickly from the atmosphere. Methane is persistent. It would last for hundreds of years in the Martian atmosphere. Without a way to take it out of the atmosphere quicker, our measurements indicate there cannot be much methane being put into the atmosphere by any mechanism, whether biology, geology, or by ultraviolet degradation [breakdown] of organics delivered by the fall of meteorites or interplanetary dust particles.” Scientists who reported finding methane argued that more research was needed to rule out the existance of microbial life.

Gravel at this site photographed by Curiosity shows evidence of an ancient streambed. (NASA/JPL-Caltech/MSSS)

The search for existing life on Mars is not quite over, however. Curiosity scientists plan to retune the SAM laboratory to enable it to detect amounts of methane of less than 1 ppb. Moreover, Curiosity’s findings don’t totally rule out the presence of life on Mars. “This important result … reduces the probability of current methane-producing Martian microbes, but … addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don’t generate methane,” said Michael Meyer, NASA’s chief scientist for Mars exploration.

The SAM laboratory findings also don’t affect efforts to determine whether life existed on Mars in the past. Only two months after landing, Curiosity found direct evidence that billions of years ago, a deep, fast-moving stream of water once flowed across Gale Crater, the rover’s landing site. This discovery showed that Mars had once been capable of supporting life. Whether it did is an open question.

Additional World Book articles:

• Mars Pathfinder
• Mars Science Laboratory
• Space exploration
• The Search for Water on Mars (a special report)

March 14, 2013

Mars once had an environment that could have been hospitable to microbial life, according to new findings by Curiosity, the most advanced rover to ever reach the red planet. The discovery by the rover, formally known as the Mars Science Laboratory (MSL), was announced by the National Aeronautics and Space Administration (NASA) this week. Since landing on Mars in 2012, Curiosity has added to the evidence from other rovers and space probes that Mars was a very different planet in the distant past than the wasteland we see today.

For its latest activity, Curiosity examined rock samples drilled from an area thought to have been part of a Martian river system at one time. The samples proved to be partially made of a type of clay that suggests conditions similar to those needed for life on Earth. Furthermore, many chemicals identified in the sample are also essential for life, including nitrates and nitrites, two chemicals used for energy by microbes on Earth.

The new findings are significant in that they show Martian water that was nearly neutral, not too acidic and not too alkaline. Earlier samples collected from other regions of the planet had found evidence of water that was less friendly to life. The discovery of nitrates and nitrites also revealed a possible source of energy for developing microbes.

A hole in a rock called "John Klein" is the site of Curiosity's first sample drilling on Mars. The drilling took place on Feb. 8, 2013. The hole is 0.63 inch (1.6 centimeters) in diameter and 2.5 inches (6.4 centimeters) deep. (NASA/JPL-Caltech/MSSS)

Many scientists think that even though the surface of Mars may not have been ideal for life, there is a possibility that life may have developed early in the planet’s history and adapted to living underground.

Additional World Book articles:

• Microbiology
• Probing the Planets (a special report)
• The Search for Water on Mars (a special report)
• Space exploration (2003) (a Back in Time article)

A new Mars rover named Curiosity lifted off for the red planet atop an Atlas 5 rocket from Cape Canaveral in Florida on November 26. The rover’s mission is to answer one of the most exciting questions in planetary science–whether Mars is, or ever has been, capable of supporting microbial life. The rover is scheduled to land on Mars in August 2012, after spending 8 ½ months traveling some 354 million miles (570 million kilometers) through space.

A channel on Mars that may have been carved by flowing water appears in this photograph from the European Space Agency's Mars Express orbiter. Images taken by the orbiter showed evidence of water on Mars both now and in the planet's past. Photo courtesy European Space Agency.

Officially named the Mars Science Laboratory, the car-sized rover carries a scientific payload about 10 times as massive as those carried by NASA’s three previous Mars rovers. Curiosity, which has been described as a self-contained geology laboratory, holds eight sophisticated instruments powered by a nuclear generator. Two of the instruments were provided by Spain and Russia. Unlike earlier rovers, Curiosity will be able to gather samples of rock and soil, process them, and then distribute them to on-board instruments. The rover is set to land in Gale Crater, near the foot of a 3-mile- (5-kilometer-) high mountain whose lower layers contain minerals that formed in water.

Scientists are anticipating the complex process of getting Curiosity onto the Martian surface as “six minutes of terror.” When Curiosity is about 1 mile (1.7 kilometers) above the surface, a rocket-powered platform called the “sky crane” will drop from the protective shell holding the rover. After flying Curiosity to Gale Crater, the sky crane will lower the rover by tether.

Additional World Book articles:

• Mars Pathfinder
• Phoenix [spacecraft]
• Space exploration (Probes to Mars)
• The Search for Water on Mars (a Special Report)