There Might Be 100 Million Planets In The Galaxy With Complex Life

What a multitude of worlds! A new study suggests that the Milky Way could host 100 million planets with complex life, leaving no lack of choice for astronomers to look for organisms beyond Earth. The challenge is, however, that these worlds might be too far away from us to do much yet.

“On the one hand, it seems highly unlikely that we are alone,” stated Louis Irwin, lead author of the study and professor emeritus at the University of Texas at El Paso. “On the other hand, we are likely so far away from life at our level of complexity, that a meeting with such alien forms is extremely improbable for the foreseeable future.”

The figure came from studying a list of more than 1,000 exoplanets for metrics such as their density, temperature, chemistry, age and distance from the parent star. From this, Irwin’s team formulated a “biological complexity index” that ranges between 0 and 1.0. The index is rated on “the number and degree of characteristics assumed to be important for supporting multiple forms of multicellular life,” the research team stated.

Assuming that Europa (a moon of Jupiter believed to have an ocean below its ice) is a good candiate for life, the team estimated that 1% to 2% of exoplanets would have a BCI that is even higher than that. So to translate that into some estimates: 10 billion stars in the Milky Way, averaging one planet a star, which brings us to 100 million planets minimum.

Goldilocks Zone
Artists impression of Gliese 581g. Credit: Lynette Cook/NSF

So what does this metric mean? There’s of course no guarantee that complex life exists in any of these places — just that the conditions could be conducive to life. Also, the researchers added, don’t assume that any life in this category would be intelligent life, but more life that is more complex than a microbe. And the known planets with higher BCIs tend to be pretty far away from us. (One of the closest is the Gliese 581 system, which is 20 light-years away.)

Read more about the research in the journal Challenges. Recall that a few years ago, this group also wrote about an “Earth Similarity Index” rating exoplanets on how close they are to our own.

“Planets with the highest BCI values tend to be larger, warmer, and older than Earth,” added Irwin, “so any search for complex or intelligent life that is restricted just to Earth-like planets, or to life as we know it on Earth, will probably be too restrictive.”

Source: Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo

Did This Martian Volcano Once Host Life?

Extremophiles teach us that life is found in unlikely places, which is why after looking at microbes happily living in hot springs or surviving after 18 months in space, scientists are trying to expand our definition of what a habitable environment is. So perhaps this ancient Martian volcano would be an example.

Meet Arsia Mons. It’s the third-tallest volcano on the Red Planet and one of the largest volcanoes we know of in the solar system.

New research shows that a combination of eruptions and a glacier on its northwest side could have formed something called “englacial lakes”, which is water that is created inside glaciers. (The researchers compare this to “liquid bubbles in a half-frozen ice cube.”) These in sum would have been massive, on the order of hundreds of cubic miles.

“This is interesting because it’s a way to get a lot of liquid water very recently on Mars,” stated Kat Scanlon, a graduate student at Brown who led the research, adding that she is also interested to see if signs of a habitable environment turn up in even older regions, of 2.5 billion years old or more.

“There’s been a lot of work on Earth — though not as much as we would like — on the types of microbes that live in these englacial lakes,” Scanlon added. “They’ve been studied mainly as an analog to [Saturn’s moon] Europa, where you’ve got an entire planet that’s an ice covered lake.”

While the glacial ice idea is not new — it’s been talked about since the 1970s — Scanlon’s team pushed the research forward by bringing in new information from NASA’s Mars Reconnaissance Orbiter.

Mars Reconnaissance Orbiter
Artist Illustration of the Mars Reconnaissance Orbiter

“Scanlon found pillow lava formations, similar to those that form on Earth when lava erupts at the bottom of an ocean,” Brown University stated.

“She also found the kinds of ridges and mounds that form on Earth when a lava flow is constrained by glacial ice. The pressure of the ice sheet constrains the lava flow, and glacial meltwater chills the erupting lava into fragments of volcanic glass, forming mounds and ridges with steep sides and flat tops. The analysis also turned up evidence of a river formed in a jökulhlaup, a massive flood that occurs when water trapped in a glacier breaks free.”

Scanlon estimated that two of the “deposits” would have had lakes of 9.6 cubic miles (40 cubic kilometers) each, while a third would have had 4.8 cubic miles (20 cubic kilometers). They could have stayed liquid for hundreds or perhaps thousands of years.

That’s a short period in the history of life, but Scanlon’s team says it could have been enough for microbes to colonize the locations, if microbes were on Mars in the first place.

You can read more about the research in the journal Icarus.

Source: Brown University

Here’s One Idea Of How To Search For Life Beyond Earth

Using a phone to search for signs of life? Yeah, we can get behind that. One group of researchers has a system that they’ve been testing out in analog environments with the aim of (eventually, one day, they hope) it being applied, say, to other planets — such as Mars.

Here’s  how it works:

“Initially the human astrobiologist takes images of his/her surroundings using a mobile phone camera. These images are sent via Bluetooth to a laptop, which processes the images to detect novel colors and textures, and communicates back to the astrobiologist the degree of similarity to previous images stored in the database,” read a press release on the technology.

View of Mars' surface near the north pole from the Phoenix lander. Credit: NASA/JPL-Calech/University of Arizona
View of Mars’ surface near the north pole from the Phoenix lander. Credit: NASA/JPL-Calech/University of Arizona

The aim is to eventually have robots, if necessary, do the same thing on Mars or in other locations. Field tests have been done in Martian analog environments, with intriguing results.

“In our most recent tests at a former coal mine in West Virginia, the similarity-matching by the computer agreed with the judgement of our human geologists 91% of the time,” stated Patrick McGuire, who works in Freie Universität’s planetary sciences and remote sensing department in Germany.

“The novelty detection also worked well, although there were some issues in differentiating between features that are similar in color but different in texture, like yellow lichen and sulfur-stained coalbeds. However, for a first test of the technique, it looks very promising.”

You can check out more details in this paper on Arxiv, a site that publishes articles before they are peer-reviewed. The information has also been accepted for publication in the International Journal of Astrobiology.

Source: European Planetary Science Congress

When We Look For Life Beyond Earth, Let’s Consider Dying Planets: Study

Bacteria. They’re so resilient that they can survive just about anywhere on Earth, even in spots of extreme hot or cold. As the sun warms up in the next few billion years, it’s likely that bacteria will be the only living creatures left on the planet, according to new research.

The study not only has implications for human survival — hopefully, our descendants will have left by then — but also our search for life on other planets. By predicting the signature these bacteria leave behind on the atmosphere, we can better hone our search for new planets, the study states.

Earth’s history shows that a species, just like an individual, can expect a lifetime that only lasts for so long. Sometimes a catastrophic event will wipe out a species, like what likely happened to the dinosaurs around 65 million years ago when a huge asteroid hit the Earth. Other times, it’s a slow process that is infinitesimal in an individual’s lifetime, but will eventually lead to changes that are unfriendly for life.

Thermophilic (heat-loving) bacteria may be among the last living creatures on Earth, the study suggests. Credit:  Mark Amend / NOAA Photo Library
Thermophilic (heat-loving) bacteria may be among the last living creatures on Earth, the study suggests. Credit: Mark Amend / NOAA Photo Library

A computer model by Ph.D. astrobiologist Jack O’Malley James, who is at the University of St Andrews, suggests the first changes will take place in only a billion years. He will present his research at the ongoing Royal Astronomical Society national meeting at St. Andrews, Scotland, which is taking place this week.

“Increased evaporation rates and chemical reactions with rainwater will draw more and more carbon dioxide from the Earth’s atmosphere,” the Royal Astronomical Society stated. “The falling levels of CO2 [carbon dioxide] will lead to the disappearance of plants and animals and our home planet will become a world of microbes.”

Earth will then run out of oxygen and begin to dry out as temperatures rise and the oceans evaporate. Around two billion years in the future, there will be no oceans left.

The Sun in H-Alpha with close-up on a rushing prominence on 02-07-2013. Credit and copyright: John Chumack.
The sun, which allows Earth to be life-friendly right now, will warm up the planet and kill off most live forms in the next few billion years. Credit and copyright: John Chumack.

“The far-future Earth will be very hostile to life by this point,” O’Malley James stated. “All living things require liquid water, so any remaining life will be restricted to pockets of liquid water, perhaps at cooler, higher altitudes or in caves or underground.”

Life would disappear almost altogether in about 2.8 billion years.

Thankfully, humans plenty of time to figure out how to get around this problem. In the meantime, we can use the knowledge when seeking life beyond Earth.

Searches these days often focus on finding life like our own, which would leave “fingerprints” behind like oxygen and ozone.

“Life in the Earth’s far future will be very different to this, which means, to detect life like this on other planets we need to search for a whole new set of clues,” O’Malley James stated. “By the point at which all life disappears from the planet [surface], we’re left with a nitrogen:carbon-dioxide atmosphere, with methane being the only sign of active life”.

More information on this research is contained in an April 2013 article in the International Journal of Astrobiology.

Source: Royal Astronomical Society