The Future for Some Habitable Moons

© Lynette Cook

Exchanging Rings?

I was watching BBC's 1999 miniseries The Planets (shown on the Science channel) recently; they were showing several episodes in a row.

In one episode they discussed how Saturn's rings will, eventually, vanish. But that the moon of another outer planet, Neptune, would break up from tidal forces as it slowly spirals in toward the planet, creating another planet with rings rivaling that of Saturn's lost rings. We would swap one ringed planet for another.

Yes, Neptune already has a ring system, but it is very dark - being comprised mostly of rocky debris while Saturn's bright rings are comprised mostly of ice. Neptune's moons are composed of rock and ice - a break up of, say Triton (one of three moons in the solar system with an atmosphere), would create a ring of ice around the planet, giving it a shimmering, shining ring system.

Spiraling Moons

This got me to thinking about the habitable moon discussions. Tidal forces are what help heat the moons (if Europa has liquid water under its icy surface, for instance, it will be the result of tidal forces). The very tidal forces that would allow for the possibility of life, which would allow for a moon to be habitable, may also signal its early demise - if the moon is slowly spiraling in.

So, for some habitable moons, their lifespans may be shorter than those of habitable planets. Which has a bearing on the rise of high order sentient life. High order sentient life probably needs a very long time to arise. Imagine being an alien race finally creating technology and exploring their solar system, only to find that their world will die long before their sun will.

Of course the flip side of the coin is shown by our moon. The Moon is slowly spiraling away from the Earth (at 3.8 centimeters, or about 2.5 inches, per year). However, while in 500 million years or so there won't be any full eclipses anymore, we won't lose the moon. Eventually the Moon and the Earth will become gravitationally locked together. At some point the Earth and Moon will become locked - the same side of the Earth will always face the same side of the moon. When that happens the Moon will quit spiraling away from us.

Why? It has to do with the fact that the Earth has large oceans. Right now the Earth rotates faster than the Moon revolves around it. The tidal bulge created by the Moon's gravitational pull moves ahead and actually forces the Moon to speed up a tiny bit. This causes its orbit to get larger. When the Earth and Moon are locked, the tidal bulge won't move faster than the Moon. High tide will be permanent in some areas, and low tide permanent in others.

"Thetis Moon" © DigitalBlasphemy.com

I still believe that we may find more habitable moons than habitable planets. But that some moons may spiral into toward their planet billions of years before their system's sun(s) die, will be one reason why it may be harder for high order sentient life to arise on some moons.

References

Cain, Fraser. "Ep. 17: Where Does the Moon Come From?" Astronomy Cast. 1 Jan. 2007. Web. 24 Aug. 2009. <http://www.astronomycast.com/solar-system/episode-17-where-does-the-moon-come-from/>

Mihos, Chris. "Neptune's Moons." Journey Through the Galaxy. Astronomy Dept. Case Western Reserve University. 13 Sept. 2006. Web. 24 Aug. 2009. <http://burro.astr.cwru.edu/stu/neptune_moons.html>

Scharringhausen, Britt. "Is the Moon moving away from the Earth? When was this discovered?" Curious About Astronomy: Ask an Astronomer. Cornell University. 21 nov. 2002. Web. 24 Aug. 2009. <http://curious.astro.cornell.edu/question.php?number=124>

The Future of Human Evolution.

I came across a Web site today which will be of some interest to those interested in speculating about alien life: The Future Human Evolution Website at <http://www.humansfuture.org/>. Yes, it is about human life and not alien life, but speculating about the future of human evolution and speculating about alien life, especially alien sentient life, overlap. If there is a Universal Biology, then examining the evolution of human life, and the future of our evolution (both natural and artificially guided) will inform our discussion and speculations on the evolution of alien sentient life.

Technology Singularity - Or, We Are Borg

The overlap is particularly salient when it comes to speculations regarding the technology singularity - when technology advances to the point that it becomes sentient. This advancement also allows sentient races who feel they have reached the limits of what biology can do for them to integrate themselves (partially or, eventually, fully) with advanced technology/machines. This is also referred to as "postbiologic." Some scientists feel this technology singularity may arrive for the human race as early as 2040, though most feel that it is more likely to be much later, the year 3000 or so.

For More Information

For more information about universal biology, visit my initial post on the topic, Universal Biologies?

For more information about postbiologic evolution or the technology singularity, visit my post Robot Aliens, The Tecnological Singularity, and Where did I leave my Borg party body?

Panspermia, Long-Lived Bacteria, and Interstellar Distances

"Dark Matter" © DigitalBlasphemy.com

I was checking out astrobiology groups on Facebook and came across a discussion on astrogensis at the "Astrobiology - Life in the Universe" Facebook group. An entry by one poster made the statement "With regards to panspermia, distances are simply too vast for living organisms to be transferred from beyond the solar system." Let's take a closer look at this problem.

The Problem

The problem stated is one of vast distances - the time for even a fast traveling extraterrestrial asteroid from even the closest star system would take an exorbitant period of time. If the average speed of an asteroid in the main belt is around 47,000 mph, and the distance to Alpha Centauri is 4.4 light-years or 25,848,247,139.8 miles (Proxima Centauri is sometimes closer, but let's go with the main star), then it would take that asteroid about 101,304 years to reach Earth.

Hardiness of Bacteria

Recently, bacteria have been found buried deep in solid rock - bacteria with very slow metabolic states and are probably thousands of years old. Penn State scientists discovered in Kalaallit Nunaat (Greenland) dormant ultra-small bacteria (Chryseobacterium greenlandensis) trapped 2 miles deep in 120,000 year old ice core samples. The scientists were able to bring them back and found it needed few nutrients to live. The scientists figure their small size helped them so survive trapped so long in the ice. Some studies indicate some bacteria can live suspended in sediments, amber, and halite for millions of years. In 2007 a group of scientists published a paper provided evidence for bacteria surviving in some frozen permafrost samples up to a half a million years. We have seen from other posts the ability for some bacteria and viruses to survive the vacuum of space. In a previous post I reported that even the small, multicellular Water Bear can survive periods in space - including normally deadly doses of ionizing radiation (Water Bears in Space!).

Illustration © European Space Organization

Spacefaring Bacteria?

With Alpha Centauri 101,304 years away (by asteroid) and bacteria that can lie dormant for at least 120,000 years (and especially those that can lie dormant for 1/2 million years), it seems that some unicellular life could theoretically make the trip. The red dwarf planetary system Gliese 581 (with one planet that is warm and terrestrial) is 20.5 light-years away, or around 471,984.5 years away at main belt asteroid velocities. Still within the range of some unicellular creatures. We have seen in earlier posts that there are scenarios where red dwarf systems can be hospitable to life.

Sol's Close Encounters

There is something else to consider as well. Our solar system is not a fixed point in the galaxy. Some researchers feel that the Sun had some close encounters with other solar systems during its 4.6 billion years of existence. The distance that a bacteria hosting extraterrestrial asteroid could have been even smaller than 4.4 light years. Some scientists feel that the Sun may have had a close encounter with another star 4 billion years ago - a very close encounter: the other star may have come as close as 14 to 19 billion miles (Neptune is 4.7 billion miles away from the Sun). That is close enough for major gravitational permutations of each solar system - including the possible exchange of an outer planet. That's right - our solar system could have, in its outermost reaches, a planet from another system left behind from this close encounter.

Let us say the other system already had life established on it. The close encounter with our Sun could cause asteroids to be jostled and sent colliding into the system's life-bearing planet, throwing up chunks of the planet into space. One of those chunks could have been captured by our solar system and eventually made it to Earth (just like some Martian "chunks" have made it to Earth, the result of some asteroid impact on the surface of Mars ejecting Martian rocks into space). Or the other system could already have asteroids with dormant unicellular life on them left over from collisions it had within itself before encountering the Sun, and one or more of those asteroids captured by our solar system.

Conclusion

In conclusion, with regards to panspermia, some stellar distances are not too vast for living organisms to be transverse and end up on Earth. Does not mean it has actually happened - the chances are still probably rather small. But the distances are not too vast, at least for stellar distances of 21 light-years or less.


References:


Coghlan, Andy. "'Resurrection Bug' Revived after 120,000 Years." Life. New Scientist. 15 June 2009. Web. 30 July 2009. <http://www.newscientist.com/article/dn17305-resurrection-bug-revived-after-120000-years.html>

"Did Our Sun Capture Alien Worlds? Close Encounter May Explain Some Objects Beyond Neptune." Science News. ScienceDaily. 9 Dec. 2004. Web. 30 July 2009. <http://www.sciencedaily.com/releases/2004/12/041208235835.htm>

Jordan, Heather. "Astrogenesis Discussion Board." Astrobiology - Life in the Universe. Facebook. 26 Mar. 2008. Web. 30 July 2009. <http://www.facebook.com/s.php?init=srp&sf=r&k=200000010&n=-1&q=life%20in%20the%20universe#/topic.php?uid=19809898338&topic=8155>

Johnson, Sarah S., Martin B. Hebsgaardt, Torben R. Christensen, et. al. "Ancient Bacteria Show Evidence of DNA Repair." PNAS. Proceedings of the National Academy of Sciences of the United States of America. 25 July 2007. Web. 30 July 2009. <http://www.pnas.org/content/104/36/14401.full>

"Novel bacterial species found trapped in Greenland's ice." Penn State Live. Penn State University. 3 June 2008. Web. 30 July 2009. <http://live.psu.edu/story/31052>

"Telepathic" DNA

© Animation Factory

Sensing Nucleotides

As reported today at Daily Galaxy, scientists reported in the ACS’ Journal of Physical Chemistry B that DNA seems to have almost "telepathic" abilities to recognize other DNA strands that are similar to it - even when there is no physical contact and no proteins to act as messengers. Similar DNA strands seem to recognize each other and gather together. There is no known chemical explanation for it. DNA strands need to recognize similar strands as part of the replication and repair processes.

Universal Biology

The reason I find this of great interest is that it adds further support that life is a natural result of the physical (and thus chemical) laws of the universe. Amino acids, which DNA are composed of, are very common in the universe - from meteors to gas clouds. If they have some innate ability to gather together, this, I feel, helps increase the chances of life arising on more than just this planet. It makes the arising of life on Earth billions of years ago, and the evolution of that life, a little less dependent upon mere luck.


Reference:

Sato, Rebecca. "Does DNA Have 'Telepathic' Powers? - Experts Say "Yes." The Daily Galaxy. 16 July 2009. Web. 16 July 2009. <http://www.dailygalaxy.com/my_weblog/2009/07/does-dna-have-telepathic-properties-research-says-yes.html>

We Choose the Moon

Source: wechoosethemoon.org

Wechoosethemoon.org is an interactive experience recreating the historic Apollo 11 mission to the Moon in real time. Once where only three men made the trip, now millions can. Live event begins 9:32 AM EDT July 16, 2009. Exactly 40 years after Apollo 11 lifted off.

Orange Dwarf Stars and Life - Common?

Illustration © European Space Organization

Our Dwarf Sun

Did you know that our own sun is in fact a dwarf star? It is a G type, or yellow dwarf. Next come the smaller K types, or orange dwarfs, followed by even smaller M types, or red dwarfs. While we know life has - at least once - arisen in a yellow dwarf system, could life arise on orange or red dwarf system? While the answer may be yest to both, some think that orange dwarfs may actually make the best place to find life.

Types of Dwarf Stars

• Yellow dwarfs (which are actually white to yellow in color), have surface temperatures of 5,000 - 6,000 K. The average size is a little larger than our sun (110% the size of the sun).

• Orange dwarfs (orange to red in color), have surface temperatures of 3,500 - 5,000 K. Their average size is about 90% that of the sun and are 40 % as luminous as the sun

• Red dwarfs (red in color), have surface temperatures below 3,500 K. The average size is about 40% that of the sun and are 4% as luminous as the sun. Red dwarfs are by far the most common star, accounting for over 75% of all the stars in our galaxy.

Habitable Zones

As you can tell, as the size decreases, the temperature decreases as well as the luminosity. The width of the Habitable Zone (HZ), thus, decreases as well and moves closer to the star (see illustration below) . But HZs still exist. And red dwarfs are extremely long lived - up to 10 trillion years - giving life plenty of time to arise. However, there are other considerations that need to be factored in. First, some tectonic activity is needed to help control the amount of C02 as well as for mixing chemicals - life needs to arise on a chemically dynamic planet. However too much tectonic activity can wipe life out. Planets orbiting in a red dwarf's HZ may experience extreme tidal forces. Another problem with red dwarfs is that being so close to the star there can be problems with radiation bursts from the star - red dwarfs tend to be rather cranky stars that frequently flare up, releasing dangerous bursts of radiation. Since the average HZ for a red dwarf is only 0.1 to 0.2 AU away, the HZ for a red dwarf may actually not be very hospitable. By the way, the HZ for yellow dwarfs, like our sun, is 0.8 AU to 2 AUs.

The average HZ for orange dwarfs is 0.3 to 1 AU away. Its HZ is wider, allowing for planets to be further from the star and thus experience less tidal forces. Also, their flare activity is only slightly more than yellow dwarfs. Another consideration is that orange dwarfs are longer lived than our sun - they have almost twice the life span: almost 20 billion years compare to the 10 billion or so years for our sun. Their light and heat output is much more stable than the sun, fluctuating less over its life and thus making more of its long lifespan useful to life. Orange dwarfs may just give life more chance to originate and thrive than yellow dwarfs like our sun. While not as common as red dwarfs (the most common star type), orange dwarfs are 3 - 4 times more common than yellow dwarfs. We definitely should not overlook orange dwarfs when searching for extraterrestrial life.

Illustration of HZs for Dwarf Stars: dM = Red Dwarfs (M class stars), dK = Orange Dwarfs (K class stars), and dG = Yellow Dwarfs (G class stars).

© Living with a Red Dwarf Program

Red Dwarf Support

Red dwarfs do have their supporters: the "Living with a Red Dwarf" Program, established at Villanova University by E. F. Guinan and S. G. Engle. Guinan and Engle, in their presentation at the 8th Pacific Rim Conference on Stellar Astrophysics in 2008, bring up an interesting consideration: the dangerous flares "are strongly dependent on rotation, and thus age, and diminish as the stars lose angular momentum and spin-down over time via magnetic braking" (Guinan 1). What this means is that the intensity and frequency of a red dwarfs solar flares may diminish over time. Since red dwarfs are extremely long lived, that does crack open just a bit further the door of opportunity for life to find a way to arise and thrive.

Phase Locked

One interesting result of a planet orbiting in an orange or red dwarf's HZ is that it will most likely be phased locked because of the tidal forces; like Mercury is to our Sun, or the Moon is to the Earth, the planet's rotational period and orbital period will be the same, resulting in the same side of the planet always facing the star. This can create a small zone along the terminator line (where, on a phase locked planet, day and night perpetually meet) where life may be able to better survive the radiation bursts.

Related Post

For an interesting related post, see the Color of Life post which tackles the question of what color would plants be on planets circling different types of stars.

References:

Guinan, E. F. and S. G. Engle. "'Living with a Red Dwarf' Program." Summary Paper. Living with a Red Dwarf. Villanova University. n.d. Web. 18 June 2009. <http://www.astronomy.villanova.edu/lward/prcsa2008_LWARD_new.pdf>

Shiga, David. "Orange stars are just right for life." Space. New Scientist. 06 May 2009. Web. 18 June 2009. <http://www.newscientist.com/article/dn17084-orange-stars-are-just-right-for-life.html>.

Another Reason Water is Important for Life

© Image courtesy NASA/MSFC

Ocean Powered Magnetism

A new theory says that salty ocean currents may be an overlooked source for the Earth's magnetic field. A magnetic field is important to protect the planet's surface from damaging ultraviolet rays. But it also protects the atmosphere from the eroding effects of the energized particles of the solar wind - though it is imperfect protection - the magnetosphere is responsible for causing some leakage by funneling some of the energy into the upper atmosphere and heating it up.

This still does not rule out life developing on desert planets, especially planets with higher gravity and thus thicker atmospheres. I wonder if a large habitable moon circling a gas giant could benefit from the giant's magnetic field?

However, if it turns out that our oceans contribute to our planet's protective magnetic shield in no small manner, then it adds impetus for us to search for planets with large bodies of water.

Tidal Mixing and the Rise of Life

Water, as mentioned in earlier posts, may also be critical when combined with tectonic activity (whether from internal forces or from external tidal forces generated from orbiting a large gas giant) to the rise of life. For example, as mentioned in an earlier post (Life Outside the "Zone"), some scientists feel that the Moon was essential to the origin of life on the Earth due to the tidal mixing which helped to mix, mainly from erosion caused by the tides, chemicals from the soil with the oceans, creating the chemical soup from which life arose.


References:

"The Earth's magnetic field remains a charged mystery." Institute of Physics News. 14 June 2009. Web. 16 June 2009. <http://www.iop.org/News/news_35352.html>.

Ryskin, Gregory. "Secular variation of the Earth's magnetic field: induced by the ocean flow?" New J. Phys. Vol. 11. 2009. (23pp) <http://www.iop.org/EJ/abstract/1367-2630/11/6/063015>.