Could Alien Life Spread 'Like a Virus' to the Stars?
In this theoretical artist’s conception of the Milky Way galaxy, translucent green “bubbles” mark areas where life has spread beyond its home system to create cosmic oases, a process called panspermia. New research suggests that we could detect the pattern of panspermia, if it occurs.
Scientists are meeting this week to discuss landing sites for NASA’s next Mars rover, an ambitious mission that not only will attempt to look for past life on Mars, but also stash samples drilled out from rocks for a future rover to retrieve and fly back to Earth for analysis. The point of the meeting is to discuss the current top candidate landing sites, though the list likely will change as new images and science data come in from satellites orbiting Mars and from NASA’s ongoing Curiosity and Opportunity rover missions.MORE: Watching the Sunsets of Mars Through Robot Eyes
The new mission, still generically referred to as Mars 2020, is due to blast off in July or August 2020 and land itself in February 2021 using a heat shield, parachutes and Curiosity’s “skycrane” tethered descent system (pictured here). Engineers also are working to develop a “terrain recognition navigation” system that would allow the descending spacecraft to take pictures and match them with imagery stored in its computer for more precise steering. That system could make many more potential landing sites safe for touchdown. Another concern is how fast the rover could traverse the surface so that it can meet its mission goals, including drilling and cache 20 samples, in one Martian year, or 668 Earth days.)
Here’s a look at some of the leading landing site contenders.
NASA/JPL-Caltech/University of Arizona
Tucked between a large volcano and an ancient impact basin is a region known as Nili Fossae, which is marked by wide, curved troughs cutting about 1,600 feet into the Martian crust. Nili Fossae is replete with clay-rich rocks, which form in the presence of water and which may be key to finding preserved organics. Nili Fossae was a top candidate for NASA’s ongoing Curiosity mission, but the site was cut due to engineering concerns.MORE: Top 10 Space Robot 'Selfies'
University of Arizona/HiRise-LPL
Scientists believe water once flowed and pooled inside an ancient crater known as Jezero, located near the Martian equator. The water streamed in from the northern and western sides of the crater, now marked by dried out channels, and eventually overflowed the crater’s southern wall, creating a third channel. Scientists do not know how long the water existed, though they do think there were at least two separate water events before the area dried out between 3.5 billion and 3.8 billion years ago. Chemical data collected by Mars orbiters show Jezero has clay and carbonate minerals that were altered by water. If life evolved during the time when Jezero was flush with water, it may be preserved in the sediments.MORE: NASA Injects New Funds Into Search for Origins of Life
NASA/JPL/University of Arizona
Ancient exposed bedrock and a diverse collection of hydratated minerals got this site a spot on the Mars 2020 candidate landing list. The targeted zone is located in the northeast part of Syrtis Major, a huge shield volcano and near the northwest rim of the giant impact basin Isidis Planitia.MORE: Alien Robots That Left Their Mark on Mars
Scientists took a long, hard look at 100-mile wide Holden Crater before deciding to send the Curiosity rover to Gale Crater instead for a mission to assess if Mars ever had all the ingredients necessary for life. That goal was met less than seven months after the rover’s Aug. 3, 2012, touchdown. Holden, along with Eberswalde Crater and Mawrth Vallis, made to the short list of Curiosity candidate landing sites and remains of interest to scientists on the follow-on Mars 2020 mission to actually look for signs of ancient life and cache samples for an eventual return to Earth.MORE: NASA Plans 'Curiosity Twin' Rover Mission in 2020
Holden Crater was once believed to have been “Holden Lake.” It contains two layers of sediments, the lower of which is believed to have formed in a large lake. The upper layer likely formed when water pooled in an area to the south known as Uzboi Vallis broke through Holdin’s rim. The current must have been strong, capable of transporting boulders dozens of feet in diameter. Within Holden’s ancient basin are numerous smaller craters, many of which are filled with sediments.
NASA/JPL/University of Arizona
The widest segment of the massive Valles Marineris canyon system is known as Melas Chasma, which cuts through layered deposits believed to be sediments from an ancient lake. Melas has hydrated sulfates and other minerals transformed by water. The southwest region contains fan-shaped structures, indicating the lake’s water level fluctuated. Another attraction is the site’s proximity to seasonal features, known as recurring slope linea, or RSL, which may be signs of present day briny water near the surface, which potentially could be explored during a mission extension.MORE: Curiosity's First Week On Mars
As astronomical techniques become more advanced, a team of astrophysicists think they will be able to not only detect the signatures of alien life in exoplanetary atmospheres, but also track its relentless spread throughout the galaxy.
The research, headed by Henry Lin of the Harvard-Smithsonian Center for Astrophysics (CfA), assumes that this feat may be possible in a generation or so and that the hypothesis of panspermia may act as the delivery system for alien biology to hop from one star system to another.
Panspermia is a process where life is somehow transplanted from planet to planet. This may happen should a planet, rich with life, be hit by a massive asteroid impact; pieces of that planet’s crust will be propelled into space and any life contained within those samples may be transplanted to another world. If these hardy lifeforms make the trip, then perhaps they can gain a foothold and seed life in this new environment.
There are other hypothetical mechanisms by which life could “hop” from one planet to the next — including the fascinating possibility of “directed panspermia” where an intelligent civilization may deliberately seed other star systems with capsules containing its biological image. Other ideas remove the need for this life to survive the trip, allowing the freeze-dried dead biology attached to space rocks to act as a template for life on a newly seeded world, a process called “necropanspermia.”
These processes are pure hypotheses right now, and this new research does not specify how life may spread, but we do know that chunks of planetary bodies can travel from planet to planet. For example, a type of meteorite found on Earth is known to originate from Mars — its isotopic signature is identical to measurements made by the armada of robots currently orbiting and roving on the Red Planet. These meteorites were bits of Mars crust blasted into space by ancient impacts.
It’s not such a stretch to think that chunks of Earth have also been blasted into space and computer simulations suggest that there’s a statistical chance that Earth rocks have drifted to the orbits of Jupiter and Saturn, potentially impacting some of the gas giants’ moons. Whether or not Earth’s abundant life was contained within these rocks is not known and it’s quite a stretch to think that a secondary genesis of life may have been spawned.
But say if life can hitch a ride on space rocks and this life can seed new biospheres on other worlds… how would astrobiologists recognize that life is being spread from one star system to the next? Well, like a common cold, the spread would appear viral.
“Life could spread from host star to host star in a pattern similar to the outbreak of an epidemic. In a sense, the Milky Way galaxy would become infected with pockets of life,” said co-author Avi Loeb, also of the CfA, in a press release.
Using a computer model, Lin and Loeb assumed that the “seeds” from one planet’s biosphere spreads in all directions over time. Should one of those seeds reach a habitable planet, there’s a chance it may take root. This creates several life-giving oases that could be detected by future space telescopes peering into these exoplanetary atmospheres. And should several of these life-endowed worlds be found, a pattern may emerge.
“In our theory clusters of life form, grow, and overlap like bubbles in a pot of boiling water,” said Lin.
According to the authors, whose paper has been accepted for publication in The Astrophysical Journal Letters (and can be viewed on the arXiv preprint service), to see any kind of “viral” pattern, life would need to spread comparatively quickly, otherwise the motion of the stars around the galaxy will blur out the pattern. If a panspermia-like spread of life is occurring in the Milky Way, it would be ideal if Earth is located on the edge of a viral “bubble”; a situation whereby all the inhabited worlds are only found in one half of the sky, whereas the other half is devoid of life despite the presence of habitable exoplanets.
The fact that we may be able to decipher the biosignatures of life in the atmospheres of distant worlds is profound enough, but should we discover clusters of inhabited worlds, it begs the question: is panspermia a viable life-spreading mechanism? But even more than that, it questions the origin of life on Earth — did life originate here? Has it spread throughout the solar system or even to other stars?
Or was Earth just in the right place at the right time to catch the virus of life?
Source: CfA press release