In the two decades since paleontologist Peter Ward and astronomer Donald Brownlee published the book, Rare Earth,1 the rare earth doctrine has become firmly entrenched in the scientific community. While many astrobiologists remain hopeful that one day we will find a planet on which microbes might reside, they acknowledge that the only place in the known universe where conditions are not hostile for intelligent life and advanced civilization is Earth.

Now, there are signs that a rare planetary system doctrine might take hold. In 1995 astronomers first discovered a planet, 51 Pegasi b, outside of the solar system that was orbiting a nuclear burning star.2 At that time, most astronomers presumed that once the list of discovered planets numbered in the hundreds or thousands, many, if not most, of those planets would manifest characteristics very similar to one of the planets in our solar system. They also assumed that we would find many planetary systems that would be carbon copies of our solar system.

Today, the list of discovered extrasolar planets stands at 3,610.3 Five orbit pulsars. The remainder orbit nuclear burning stars. The masses of the planets orbiting nuclear burning stars range from 2% of Earth’s mass to more than 20 times the mass of Jupiter. For comparison, Mercury’s mass = 37% of Earth’s mass and Jupiter’s mass = 318 times that of Earth’s mass.

The only extrasolar planet that comes close to matching the characteristics of a solar system planet is Upsilon Andromedae e. Its mass compared to Jupiter’s is 1.06+ (because the inclination of Upsilon Andromedae e’s orbit is not known, only a minimum mass has been determined). Its distance from its host star compared to Jupiter’s distance from the Sun is 1.01. Like Jupiter, Upsilon Andromedae e has a nearly circular orbit about its host star.

Several features of Jupiter that are critical for life on Earth, however, are not shared by Upsilon Andromedae e. For example, Jupiter is the closest to the Sun of all the solar system gas giant planets and it possesses more than twice the mass of all the other solar system planets combined. Upsilon Andromedae e, though, is accompanied by two much larger planets, Upsilon Andromedae c and d, with masses = 14.57+ and 10.19+ times greater than Jupiter’s, respectively. These two planets orbit the system’s host star 6.1 and 2.1 times closer, respectively, than does Upsilon Andromedae e. Their orbits also are highly eccentric (elliptical). Moreover, the host star is 1.28 times more massive and 3.4 times more luminous than is the Sun. The system includes a dim star orbiting the main star at 750 times farther away than Earth orbits the Sun. The characteristics of both the main star and the two heavy planets accompanying Upsilon Andromedae e rule out the possibility that another planet in the same system could possibly support advanced life.

The extrasolar planetary systems discovered so far look nothing like the solar system. The norm for these systems is that they are populated with hot and warm gas giant planets—that is, with planets ranging from the mass of Uranus (14.5 times Earth’s mass) to many times the mass of Jupiter that orbit their host stars significantly closer than Jupiter orbits the Sun. Their proximity to their host stars rules out the possibility of any kind of advanced life on a rocky planet in the same system.

These planetary systems also frequently contain one or more super-Earths, planets ranging in size from 1.5–10 times Earth’s mass and that orbit their stars equal to or less than Earth’s distance from the Sun. Furthermore, whereas the known extrasolar planetary systems are filled with many planets possessing high-eccentricity orbits, the solar system has only one—diminutive Mercury, which resides so close to the Sun as to pose no risk of disturbing any of the other seven solar system planets.

Astronomers now have a good understanding of why the solar system seems unique. For most planetary systems, the larger planets form far from their host stars and migrate into close orbits about their host stars. For the other known extrasolar planetary systems, the larger planets either do not migrate at all or migrate only short distances toward their host stars. By contrast, the large planets in the solar system performed a “Grand Tack” migration. I discussed the amazing fine-tuning of the Grand Tack migration of Jupiter, Saturn, Uranus, and Neptune in a recent blog post.4

Thanks in large part to research on extrasolar planets, astronomers also know that every planet in the solar system fulfills a key role in making advanced life possible on Earth. Two Brazilian astronomers showed that even tiny adjustments in the orbits of Jupiter, Saturn, Uranus, and Neptune would prove catastrophic for life in our solar system.5 Regions beyond the precise orbital positions of Jupiter, Saturn, Uranus, and Neptune abound in destructive mean motion resonances. As it is, Uranus is close to a 7:1 resonance with Jupiter (where Jupiter would make exactly 7 orbits around the Sun for every single orbit of Uranus), a 2:1 resonance with Neptune, and a 3:1 resonance with Saturn. Meanwhile, Jupiter and Saturn are very close to 5:2 resonance. If any of the solar system gas giant planets’ orbital positions were to shift ever so slightly, that shift would destabilize the orbit of one or more of the eight planets in the solar system with catastrophic consequences for a long history of life on Earth.

Three Canadian astronomers further demonstrated that the orbital positions of Venus, Earth, and Mars must be fine-tuned so as to break up mean motion resonances that could be damaging for life on Earth. They showed that even the orbital features of the Earth-Moon system must be fine-tuned for this purpose.6 The Earth-Moon system suppresses a resonance in Venus’ orbit that is generated from the orbital patterns of Jupiter, Saturn, Uranus, and Neptune. Unless the Earth-Moon system is configured the way it is, both Venus’ and Mercury’s orbits would destabilize and generate destructive chaos throughout the inner solar system.

Every planet in our solar system and Earth’s Moon contribute to making advanced life possible on Earth. The solar system’s array of eight planets must be exactly the way it is. Have you thanked God today for Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune?

Featured image: The Sun’s eight planets  are shown to approximate size scale relative to the Sun. The distances are not to scale. 

Endnotes

  1. Peter D. Ward and Donald Brownlee, Rare Earth: Why Complex Life Is Uncommon in the Universe (New York: Copernicus, 2000).
  2. Michel Mayor and Didier Queloz, “A Jupiter-Mass Companion to a Solar-Type Star,” Nature 378 (November 23, 1995): 355–59, doi:10.1038/378355a0.
  3. “Catalog, Exoplanet TEAM, The Extrasolar Planet Encyclopaedia, last modified June 8, 2017, http://exoplanet.eu/catalog/.
  4. Hugh Ross,Grand Tack Model Reveals More Solar System Designs, Today’s New Reason to Believe (blog), Reasons to Believe, May 22, 2017, http://www.reasons.org/blogs/todays-new-reason-to-believe/grand-tack-model-reveals-more-solar-system-designs.
  5. T. A. Michtchenko and S. Ferraz-Mello, “Resonant Structure of the Outer Solar System in the Neighborhood of the Planets,” Astronomical Journal 122 (July 2001): 474–81, doi:10.1086/321129.
  6. Kimmo Innanen, Seppo Mikkola, and Paul Wiegert, “The Earth-Moon System and the Dynamical Stability of the Inner Solar System,” Astronomical Journal 116 (October 1998): 2055–57, doi:10.1086/300552.

Subjects: Astronomy, Exoplanets, Planets, Solar System Design

Check out more from Dr. Hugh Ross @Reasons.org

About The Author

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.



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