The atmosphere of Mars was altered when Comet C/2013 A1, aka Sliding Spring, deposited large amounts of dust and ice on Mars. Comets may be the transportation system of the universe. They carry ancient minerals and water as they fly vast distances, leaving a trail of debris in their wake.
Sliding Spring will take about one million years to complete its circle around the sun. It originated in the Oort Cloud at the far limits of the solar system. The Oort Cloud is a distant region, between 5,000 and 100,000 AUs from the Sun. It consists of trillions of icy objects made up of material that was barely caught in the gravitational pull of the sun. In fact, the Oort Cloud is influenced by the pull of nearby stars and the Milky Way disc. Occasionally, objects in the Oort Cloud are knocked loose and begin to fall towards the center of the solar system. They become comets with large, elliptical orbits that loop around the sun. As they near the inner solar system, the sun’s heat melts off some of the ice and dust and the comet forms an atmosphere, or coma, that may be hundreds of thousands of miles wide.
Astronomers were able to observe an object from the Oort Cloud for the first time last month as Sliding Spring buzzed past Mars and Earth on its way to loop around the sun. Traveling at 35 miles per hour, it passed quite close to the red planet and showered Mars with cometary ice and dust. The meteor storm triggered by the comet actually changed the composition of the atmosphere of Mars. Coming straight from the Oort cloud, the pristine comet carried material from the creation of the Solar System. It came within 87,000 miles of Mars, close enough that its coma collided with Mars. As the coma hit the upper atmosphere of Mars it released tons of cosmic dust. Thousands of fireballs per hour streaked across the Martian sky. The amount of dust deposited by the comet warped the atmosphere of Mars. Jim Green, the director of NASA’s Planetary Science Division, described the event, saying “The comet’s dust slammed into the upper atmosphere, creating a massive and dense ionospheric layer, and literally changed the chemistry of the upper atmosphere.”
Astronomers used data collected from various orbiting spacecraft to examine the extent and brightness of the ultraviolet emissions left from the collision. At least a few tons of dust covered nearly half the planet. The comet had a much more extensive effect on Mars than scientists expected. Fortunately, spacecraft were moved to the far side of Mars and survived the dust storm while still able to collect information. NASA’s Mars Odyssey, Mars Reconnaissance, and MAVEN, along with India’s Mars Orbiter and the European Space Agency’s Mars Express, all weathered the event intact. Hiding the spacecraft saved them from destruction. Scientists have been poring over the data collected since the Sliding Spring’s visit to Mars on Oct. 19. NASA’s two Mars rovers, the Curiosity and the Opportunity, also witnessed the comet. The rovers are not equipped with video cameras but stills were put together to recreate the comet’s journey.
From the data the orbiting spacecraft gathered, astronomers have found at least eight metals were transferred to the atmosphere of Mars. A large amount of magnesium ionized the upper atmosphere with extra electrons. Iron, potassium, chromium, manganese, nickel and zinc were left behind. Sodium most likely caused the Martian atmosphere to glow yellow until it dissipated. The metals are expected to condense into meteoric smoke which could form high-altitude clouds and interact with sunlight reaching Mars. The chemistry of the atmosphere could have been permanently altered.
Sliding Spring had a similar effect on Earth, although to a lesser extent. On Oct. 25 the comet passed by at a distance of 130,000 million miles. Astronomers recorded a five to tenfold increase of electrons in the ionosphere. Although Sliding Spring itself did not come very close to Earth, the debris deposited in the atmosphere of Mars could provide clues about how some water and metals could have arrived on Earth.
It is rare that on object from the Oort cloud comes into the inner solar system. Rarer still is how close it came to a planet without a devastating collision. Astronomers were able to use modern technology to study the comet and its effect on the Red Planet. The upper atmosphere of Mars was altered by cosmic dust and ice as Sliding Spring brushed by on its orbit around the sun.
By: Rebecca Savastio