NASA’s MAVEN mission providing insights into life on distant worlds
Mars. Long a destination dreamed of by the public in general and space enthusiasts in particular, is providing insights about the length of time that other planets can support life. How long would a planet like Mars, orbiting a distant red dwarf star be habitable? One of NASA’s Scout Program missions is helping to develop an answer.
To provide a better understanding of these dynamics, NASA has tapped its Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft to provide data for scenarios about the habitability.
“Habitability is one of the biggest topics in astronomy, and these estimates demonstrate one way to leverage what we know about Mars and the Sun to help determine the factors that control whether planets in other systems might be suitable for life,” said Bruce Jakosky, MAVEN’s principal investigator via a release issued by NASA.
It is not known if a world similar to Mars would be able to remain habitable. There are a lot of variables which come into play and NASA is using MAVEN, currently in orbit above the surface of the Red Planet to provide some clues.
“The MAVEN mission tells us that Mars lost substantial amounts of its atmosphere over time, changing the planet’s habitability,” said David Brain, a MAVEN co-investigator and a professor at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. “We can use Mars, a planet that we know a lot about, as a laboratory for studying rocky planets outside our solar system, which we don’t know much about yet.”
Brain noted how MAVEN was being used to better determine the habitability of distant worlds during the fall meeting of the American Geophysical Union on Dec. 13, 2017, in New Orleans, Louisiana.
MAVEN is well-equipped to carry out such an endeavor, the spacecraft has a suite of instruments on board that have been used to monitor the loss of Mars’ atmosphere. The probe has been conducting its studies since November of 2014, after reaching Mars orbit two months earlier.
A mixture of chemical and physical processes have stripped the Red Planet of its atmosphere and MAVEN’s science instruments are keeping an eye on how this loss continues to this day.
MAVEN was initiated as part of NASA’s Mars Scout Program which included the Mars Phoenix Lander in forays to the Red Planet. NASA’s Mars Scout Program was discontinued in 2010.
As the term “scout” implies, the missions were relatively low cost, with missions targeted at costing no more than $485 million (not including the cost of launch services). With the cost to launch on United Launch Alliance (ULA) rockets estimated at costing some $187 million, the missions cost around $671 million (as was noted by National Geographic).
Since it began its study of Mars, MAVEN has been able to study the planet as it encountered solar storms and flares as well as coronal mass ejections – all of which have a major impact on the tenuous Martian atmosphere (which is about 1 percent of Earth’s and comprised mostly of carbon dioxide).
With these studies underway, Brain and his fellow researchers, began studying what similar worlds that orbit distant “M-stars” or around red dwarf stars (the most common class of star in the Milky Way Galaxy) might encounter.
Scientists used Mars as a baseline, however, as red dwarf stars are far dimmer than our Sun, these hypothetical worlds would have to orbit closer to their parent star than Mercury does to the Sun (some 36 million miles or 58 million kilometers).
Studies suggest that the brightness of a red dwarf at ultraviolet (UV) wavelengths when coupled with these worlds’ close orbit to its star – that it would receive approximately 5-10 times as much UV radiation as Mars presently does. Scientists believe this would increase the amount of energy that drives atmospheric escape. Estimates suggest that the rate of loss of charged particles would be 3 to 5 times greater if a planet similar to Mars was in the habitable zone around one of the aforementioned stars. On top of that – 5 to 10 times more neutral particles would be lost via a process called photochemical escape. This occurs when UV radiation breaks apart molecules in a planet’s upper atmosphere.
This also helps fuel another process, known as “sputtering” as these molecules break apart – they knock other molecules around and some are bumped out into space or crash into nearby molecules.
But that is not all.
These, as of now, hypothetical worlds, would also encounter similar amounts of thermal or “Jeans” escape. This only takes place with lighter molecules like hydrogen which the Red Planet loses from the top of its atmosphere. Scientists believe this would only take place on these exoplanets if UV radiation were to push hydrogen to the top of that planet’s atmosphere.
Estimates suggest that these processes, when combined, would reduce the potential habitable “life” of one of these planets by a factor of about 5 to 20. This of course depends on the level of activity of the star that these planets orbit, with the habitable period potentially being cut by as much as 1,000 and with solar storms bathing the world in radiation, the likelihood of life gaining a foothold diminishes significantly.
Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.