By ELIZABETH LIU
Senior Staff Writer
Scientific data have suggested for several years that Mars may have a tiny amount of liquid water in its mostly dry and arid landscape. New evidence from pebbles in ancient riverbeds suggests that three billion years ago Mars had an extensive river system that carried these rocks for miles.
This data was collected by the NASA’s Curiosity rover, which landed on the Red Planet in August 2012. The Mars Science Laboratory, an onboard laboratory attached to the rover, is considered one of the most ambitious Mars missions yet.
The goal of NASA’s mission is to find out whether the planet ever had an environment able to support life. While Curiosity is not designed to find life, the rover is equipped with advanced instruments that allow it to collect information about its surrounding environment. Its seven-foot-long arm can drill into rocks, scoop up soil and deposit samples into the rover’s oven.
While the sample is baking, sensors can analyze the gases from the heated compounds and determine its chemical composition, giving us an idea of what the planet’s environment was like in the past. Its high-resolution camera can capture the landscape as the rover moves, providing images of landscapes that can be compared to Earth’s different environments.
In early 2013 Curiosity sent back data that suggested that Mars had habitable living conditions in the past — powder from the first drill and soil samples included carbon, hydrogen, oxygen, nitrogen, phosphorous and sulfur, all of which are considered fundamental building blocks that could support life.
In the same year, the rover also discovered the existence of small, round stones near its landing site in the Gale Crater. The researchers noticed that the stones had an uncanny resemblance to those found in riverbeds on Earth, which become rounder and smoother the more they roll and collide with other rocks.
Evidence now suggests that the smooth pebbles found on Mars could have been rolling in the Red Planet’s (now non-existent) rivers for quite a while. In a report published in Nature Communications, researchers from the University of Pennsylvania and the Budapest University of Technology and Economics describe the first-ever method developed to quantify and estimate the transport distance of rocks in rivers by only using data collected from the pebbles’s shapes.
This model is based on the discovery and concept of the Gömböc, a three-dimensional object with only two static balance points. A Gömböc object can self-right itself on a horizontal surface based on shape alone. During natural abrasion, such as the erosion found in river systems and running water, the number of static balance points in an object is normally diminished.
Since the Gömböc has only two static balance points, its shape represents the ultimate goal of erosion and other natural abrasion processes. Therefore, the researchers decided to base their model on pure mathematics to describe the geometry and mass of eroded three-dimensional structures. However, since the rover did not record the masses of the Martian pebbles, the researchers had the much harder task of determining the amount of mass lost by each pebble solely based on shape.
To confirm that their method was viable, the researchers first tested their theory in a lab by rolling rock fragments in a drum and periodically recording their shape and their lost mass. They also had a chance to test their theory in the field by collecting rock and pebble samples from a mountain river in Puerto Rico. In the end, the researchers found that the actual pattern of the rocks’ shape change closely followed that of their predictive model.
In order to determine the distance that a pebble traveled, the researchers traced the contours of the pebbles found in NASA’s publicly available images. Their model suggests that the pebbles on Mars had lost approximately 20 percent of their original mass and had traveled about 30 miles from their sources, suggesting that the planet had an extensive river system that could have possibly supported life.
The researchers hope that their model will not just be used for extraterrestrial analyses. The concept could even be used for studies on Earth — scientists could potentially identify the source of a river-transported resource, such as gold, by measuring the object’s dimensions.