Exomoons Could Be Excellent Incubators

Article written: 18 Jun , 2011
Updated: 24 Dec , 2015
by

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With the arrival of the Cassini–Huygens mission in 2004 to Saturn’s satellite Titan, we terrestrials became acutely aware that similar moons could be orbiting similarly large planets in other solar systems besides our own. These extrasolar moons, or exomoons, might be a little bit difficult to distinguish with our current equipment, but our technological grasp has greatly improved in recent years. Now current studies suggest that not only can these naturally occurring satellites exist – but they also might be habitable.

As we know, there isn’t exactly a lack of planetary candidates hospitable to life. At least 40 so far discovered are within Earth-like tolerances and it’s only a matter of time before transit timings (TTV and TDV) and wobble variations will allow us to detect their moons. If the potential is there for the giant planet – then why not its companion?

“The satellites of extrasolar planets (exomoons) have been recently proposed as astrobiological targets. Since giant planets in the habitable zone are thought to have migrated there,” says Simon Porter of Lowell Observatory and William Grundy of Arizona State University. “It is possible that they may have captured a former terrestrial planet or planetesimal.”

Although we’re aware of life-possible exoplanet existence, we’re not yet sure of how they got to their current position. Simulations show they may have formed on the edge of where ice can exist, but this might also make them a bit inhospitable. Disk migration would bring them closer to the parent star – but also make them intolerably hot. Yet, there’s a theory which says during the shuffle that some planetesimals could have been “swapped” in the process.

“We therefore attempt to model the dynamical evolution of a terrestrial planet captured into orbit around a giant planet in the habitable zone of a star.” says Porter and Grundy. “We find that approximately half of loose elliptical orbits result in stable circular orbits over timescales of less than a few million years. We also find that those orbits are mostly low-inclination, but have no prograde/retrograde preference.”

Right now the most probable candidates for “living” exomoons would be around planets very similar to Neptune and orbiting a star similar to our Sun. Once these Earth-massed satellites have stabilized into a long-lived orbit, they should be within the range of findability using the transit timing variation much stronger than the duration variation – even if their orbit is tight to the parent planet.

“In addition, we calculate the transit timing and duration variations for the resulting systems, and find that potentially habitable Earth-mass exomoons should be detectable.” reports the team. “Even with these closer orbits, some exomoons are still within the range of detectability. The combination of TTV and TDV may offer a stronger detection signal than photometry for these orbits, though both could detect some of the orbits produced.”

Abstract Information: Post-Capture Evolution of Potentially Habitable Exomoons.


10 Responses

  1. Sassan says

    Let’s get to Europa and find life there too!!

  2. Anonymous says

    “Although we’re aware of life-harboring exoplanet existence,”
    We are?

    • Member
      Tammy Plotner says

      nice catch! another example of my brain moving faster than my fingers… 😉

      it has been changed to “life-possible”.

      • IVAN3MAN_AT_LARGE says

        Like also at the first paragraph, there’s a missing adverb “not” in the last sentence: “Now current studies suggest that [not] only can these naturally occurring satellites exist – but they might be habitable.” 😉

      • Member
        Tammy Plotner says

        thank you, i3m! you are very correct and the changes have been made. i appreciate your suggestions. i work about 12 hours a day writing text, so doing a UT article is like wonderful “mind candy”. i enjoy the heck out of researching, (and will often get lost for hours reading abstracts) then my brain is so full that i’ll “see” words that aren’t there. while my formal job allows me a bit more wiggle room to spot my errors when re-reading at a later date – the readers here tend get me a little more “naturally”… as i would talk to friends about something new i had read. the major difference is these words hang around permanently in the air for all to see, so please let me know when i’m being “air-headed”!

        😀

      • Member
        Tammy Plotner says

        thank you, i3m! you are very correct and the changes have been made. i appreciate your suggestions. i work about 12 hours a day writing text, so doing a UT article is like wonderful “mind candy”. i enjoy the heck out of researching, (and will often get lost for hours reading abstracts) then my brain is so full that i’ll “see” words that aren’t there. while my formal job allows me a bit more wiggle room to spot my errors when re-reading at a later date – the readers here tend get me a little more “naturally”… as i would talk to friends about something new i had read. the major difference is these words hang around permanently in the air for all to see, so please let me know when i’m being “air-headed”!

        😀

      • IVAN3MAN_AT_LARGE says

        Thanks for your appreciation, Tammy! I also appreciate your efforts in taking the time to write articles for Universe Today, which I enjoy reading as much as I do with Nancy’s and other authors’ articles on UT.

        Yeah, I know it’s difficult to proofread your own work; I also usually put aside an essay/letter/what-have-you that I’ve written until the next day — when I get up at 2:00 p.m.! Then I can check it more thoroughly after I’ve had a mug of strong, black coffee! Sure enough, I then easily spot typographical/grammatical/punctuation errors that I had not spotted earlier; it’s something to do with the change of perspective — and that is why we have peer review in science!

      • Anonymous says

        Great article, Tammy! One of my favorite subjects. Thanks again. Dan

  3. oscar gu says

    gracias por enseñar lo que no vemos y hacer de nuestra conciencia mas acrecentada y satisfacer la existencia de lo bello del universo saludos

  4. David King says

    Just this morning finished a book (for the 6th time in 21 years!) by Isaac Asimov called “Nemesis”. I mention it because it is relevant to this article of habitable exomoons orbiting gas giants.

    He published this book in 1989! So the idea of a habitable exomoon has been around for many years! I’ve just remembered that in Star Wars there was a habitable exomoon as well!

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