Volcanoes May Have Warmed Mars Enough for Water
Eruptions could have kept planet warm enough for liquid water to intermittently flow across its ancient surface, suggests a new study.
Volcanic eruptions could have kept Mars warm enough for liquid water to intermittently flow across its ancient surface, suggests a new study.
The new findings, reported in Nature Geoscience, could explain the discrepancy between climate models showing Mars was never capable of having liquid water on its surface, and clear geological signatures of lake beds and river valleys formed by flowing water.
"There's indisputable evidence that Mars was once warm enough for liquid water to flow on its surface," says one of the study's authors, Professor James Head of Brown University in Providence Rhode Island.
"It's difficult to reconcile this fact with the latest generation of very robust climate models, showing Mars was always very cold and very icy, with an atmosphere too thin to heat the planet enough for water to flow."
The picture of a warmer early Mars is further complicated by the Sun also being much dimmer billions of years ago than it is today.
Head and the study's lead author Dr Itay Halevy of the Weizmann Institute in Tel Aviv, found there was a huge increase in volcanic activity on Mars about 3.7 billion years ago, the same time as water flowed on the red planet's surface, forming river valleys, deltas and lakes.
Significant volcanic eruptions on Earth can cause cooling rather than warming, as sulfuric acid particles and thick ash plumes either absorb solar radiation or reflect it back into space, lowering temperatures.
But dust in the Martian atmosphere mitigates the cooling effect, says Head.
"We looked at Mars' early atmosphere being dusty, and our calculations suggest a lot of the [volcanic plume] minerals like sulfur dioxide and sulfuric acid will adhere to these dust particles, reducing their ability to reflect the Sun's rays, delaying cooling," he explains.
The authors found brief periods of intense volcanic activity would have pumped significant levels of greenhouse-inducing sulfur dioxide gas into the atmosphere, warming the Martian equatorial region sufficiently for liquid water to flow.
"We calculate that 30 per cent of Mars was resurfaced by lava flows, that's a lot of lava, and it can erupt over relatively short periods of time," says Head.
"It comes out as flood basalts and can have a huge affect on a planet's atmosphere."
Similar flood basalt formations on Earth, such as India's Deccan traps, and the Siberian traps in Russia, covered thousands of square kilometres, and are thought to have been caused by deep mantle plumes.
"If you bring the temperature up above freezing for decades to centuries, that melts enough ice and snow to produce the geological features we see in Martian valley networks and open basin lakes, even in a cold and icy early Mars," says Head.
Head thinks the climate on early Mars may have some similarities to the cold, desert-like McMurdo dry valleys he's studied in Antarctica.
"The average yearly temperature in the Antarctic dry valleys is way below freezing, but peak summer daytime temperatures can exceed the melting point of water, forming transient streams, which then refreeze," says Head.
"In a similar manner, we find that volcanism can bring the temperature on early Mars above the melting point for decades to centuries at a time causing episodic periods of stream and lake formation."
The research may provide new clues about where to look for the fossilised remnants of any life forms that might once have existed on Mars.
"Microbial algae matts in Antarctica are resistant to the solar radiation and extreme cold and dry conditions," says Head.
"They sit there and just wait for the water to come, and when the water does come, they burst into bloom, so to speak. At other times they just dry up and get blown about to new locations by the wind where they wait for more water.
"Thus, the ancient and currently dry and barren river and lake floors on Mars may harbor the remnants of similar primitive life, if it ever occurred on Mars."
Mars as observed by the Hubble Space Telescope in 1997.
Since NASA's Mars Science Laboratory (MSL) rover Curiosity landed on the red planet, each sol (a Martian "day") of the mission sees a flood of new photographs from Aeolis Palus -- the plain inside Gale Crater where Curiosity landed on Aug. 5. In September 2012, mission controllers sent the command for Curiosity to flip open the dust cap in front of the robotic arm-mounted Mars Hand Lens Imager (MAHLI). Until that point, the semi-transparent dust cap only allowed MAHLI to make out fuzzy shapes -- although it did a great job imaging Curiosity's "head" and it is also famous for capturing Curiosity's first color photograph. But since the true clarity of MAHLI has been unleashed, we've been treated to some of the most high-resolution views of the rover, Martian landscape and, most importantly, we've seen exactly what MAHLI was designed to do: Look closely at Mars rocks and dirt, assembling geological evidence of potential past habitability of Mars.
The Business End
Curiosity is armed with 17 cameras and MAHLI is designed to capture close-up photos of geological samples and formations as the rover explores. MAHLI was designed and built by Malin Space Science Systems and is analogous to a geologist's hand lens -- only a lot more sophisticated. Its high-resolution system can focus and magnify objects as small as 12.5 micrometers (that's smaller than the width of a human hair!). This photograph captured by the rover's Mastcam shows the MAHLI lens (with dust cap in place) in the center of the end of Curiosity's instrument-laden robotic arm.
To aid its studies, MAHLI is equipped with four LEDs to light up the imager's samples.
The first photograph to be returned from MAHLI without the dust cover in place was received on Sol 33 (Sept. 8) of Curiosity's mission. Shown here is a view of the ground immediately in front of the rover. Although this photo was a test, mission scientists were able to do a very preliminary study of the large "pebble" at the bottom of the picture: "Notice that the ground immediately around that pebble has less dust visible (more gravel exposed) than in other parts of the image. The presence of the pebble may have affected the wind in a way that preferentially removes dust from the surface around it," they wrote.
How Did Lincoln Help MAHLI?
On Sol 34 (Sept. 9), MAHLI was aimed at Curiosity's calibration target. This target is intended to color balance the instrument and provide a "standard" for mission scientists to refer to. The 1909 Lincoln penny was provided by MAHLI's principal investigatory Ken Edgett. Using a penny as a calibration target is a nod to geologists' tradition of placing a coin or some other object of known scale as a size reference in close-up photographs of rocks, says the MSL mission site.
Although MAHLI will be used to examine microscopic scales, it is showing its prowess at generating some spectacular high-definition views of the rover. Shown here is a mosaic of Curiosity's three left-side dusty wheels.
Hazard Avoidance Cameras
Hazard Avoidance Cameras, or Hazcams, have become "standard issue" for the last three rovers to land on Mars. Mounted on the front and back of rovers Opportunity, Spirit and Curiosity, these small cameras provide invaluable information about the terrain and potential hazards surrounding the rovers. These cameras are not scientific cameras -- they are engineering cameras. Shown here, MAHLI has imaged the four front Hazcams on Curiosity. Interestingly, it was these cameras who returned Curiosity's first dusty image after touch down in August.
Using the flexibility of the robotic arm, MAHLI was able to check the underside of Curiosity. As the camera can focus on objects from 0.8 inch (2.1 centimeters) to infinity, MAHLI has incredible versatility allowing mission controllers to focus on the very small features of Mars to checking the health of the rover to viewing the impressive vistas beyond.
In October 2012, the Internet was abuzz with speculation about a "mystery object" lying beneath the rover during digging operations at "Rocknest." Sadly, after studying the translucent object, mission scientists deduced that it wasn't anything native to the alien environment, it was actually a piece of plastic that had fallen from Curiosity. Yes, Curiosity is littering the red planet.
The MAHLI camera was very attentive while Curiosity dug trenches in the Mars soil at "Rocknest."
In early 2013, MAHLI snapped another curious photo. This time, after driving to a rocky outcrop at a location dubbed "Yellowknife," the camera picked out what appeared to be some kind of organic-looking object embedded in the rock. Nope, it's not a Mars "flower" -- more likely it's a concentration of minerals.
In what has become an iconic photo of Curiosity, MAHLI was commanded to capture dozens of high-resolution pictures of the rover. Like an "arms length" shot you may have in your Facebook profile, Curiosity did the same, composing a mosaic of pics taken with its outstretched robotic arm.
Curiosity Cleans Up!
The Mars rover isn't only a scientific superstar, it also has a talent for cleaning. This circular pattern on a Mars rock was brushed aside by Curiosity's Dust Removal Tool (DRT), helping the rover carry out analysis of the rock surface beneath the layer of dirt.