August 11, 2017 | Henry Richter

Facing Reality About Life on Other Planets

by Dr Henry Richter

For a number of years I have been amused to watch many in the scientific community conduct a frantic campaign to identify life elsewhere in the universe. There has been a plethora of articles and significant dollars dedicated to the search for extraterrestrial life, particularly intelligent life. In recent times several thousand planets have been discovered orbiting stars throughout the visible universe. Several large radio telescopes have been conducting searches for coherent radiation that originated outside of our galaxy. A number of scientific instruments have flown on unmanned spacecraft looking for life forms or related chemicals in our local planetary exploration.

A recent article in EOS Earth & Science News discusses “Ten Earth-Sized Planets Found by Exoplanet-Hunting Telescope.” Now, the way that distant planets are detected is that when they pass in front of their host star that they cause a minuscule dimming of the light from that star. No information about the new planet is forthcoming at this point except an estimate of its size and of its orbital parameters around its host star.  No atmosphere, no oceans, no type of surface, no core, no magnetic field, no rotation rate, etc. can be inferred.

It is certainly no surprise to find planets orbiting stars. This is to be expected in the universe. There is no rationale that would say that our sun is the only object in the universe surrounded by planets. It is a big leap beyond that conjecture to think that life abounds on these planets around other stars. So I would like to explore a number of  features and characteristics of the planet that will allow life to exist. We, of course, will start with the earth as an example of a planet where we know life exists. We can list a number of features and characteristics that allow life to exist here and which if just one were not present, would make life impossible.  So let me list a number of these features, and we will examine them in more detail in this and future issues of this series.  Many of these insights I have gathered from the excellent video “The Privileged Planet” produced by Illustra Media.

  • A location in a “safe” place in the galaxy, not close to any active regions, overactive stars, or black holes
  • Being attached to a stable star.  Our sun, a G2 type is ideal
  • Having our host star the proper size, and with proper stable energy output
  • Being in an orbit in the “habitable” zone setting temperature in a fairly narrow region
  • Having several gas giant planets in the system for protection from orbiting debris
  • Having a near-circular orbit assuring that the heat input from the star does not vary much
  • A planet with the proper inclination as it goes around its orbit
  • Having a planet within a certain range of masses
  • Having a planet with a reasonable rotation rate
  • Having an atmosphere with the right composition and density
  • Having liquid water of the proper amount and composition
  • Having a good ratio between water (oceans) and land
  • Having hydrogen with specialized bonding to give water characteristics different than other substances
  • Having a satellite moon of the right size and distance
  • A planet of the proper mass
  • A planet with a liquid iron core to generate a magnetic field
  • A planet with a magnetic field of the proper strength
  • A rocky planet with a crust of the proper thickness to allow plate tectonics to occur
  • A planet with a good source of carbon – in the form to allow chemical reactions
  • A planet with a number of rare element chemicals which are essential to life forms

Let me start with the first: location within the parent galaxy.  We ride in the Milky Way galaxy, about half way between the center and the edge.  That is a safe place to be, as the center has all sorts of things going on such as black holes and supernovae.  The center is a place with a high radiation environment which would be destructive to life, and even to basic chemistry processes.  On the other hand, being close to or at the edge of the galaxy would be in a region of low density of materials, probably not enough to collect into a planetary body.  The half-way position results in a reasonable sized habitable zone around stars.

Our galaxy has spiral arms, and we don’t want to be located in one of those.  We are between the Sagittarius and Perseus arms of the galaxy.  These are regions of star building activity, where we do not want to be. We are in a nice safe gap between the arms.

And one comment about our galaxy which does not impact its livability, although our galaxy is huge in extent, it is quite flat and has narrow thickness.  This puts us in an excellent place for astronomical observations.  We do not have much dust to peer through. We are far enough from the bright center of the Milky Way to be able to see outside our galaxy, and to be able to discern and identify other galaxies and their constituent stars.  So not only do we live in a place which permits life, it also is an excellent place to be able to conduct scientific research, and to develop some understanding and appreciation of the universe and all the marvels of nature. This is an added benefit of being alive.

In subsequent articles, I will march down the list of features listed above and have a brief discussion of how these become crucial to the existence of life, and how this affects our search for life elsewhere in the universe.

Image credits: Illustra Media, The Privileged Planet

Dr Henry Richter, a contributor to Creation-Evolution Headlines, was a key player at NASA/JPL in the early days of the American space program. With a PhD in Chemistry, Physics and Electrical Engineering from Caltech), Dr Richter brings a perspective about science with the wisdom of years of personal involvement. His book America’s Leap Into Space: My Time at JPL and the First Explorer Satellites (2015), chronicles the beginnings of the space program based on his own records and careful research into rare NASA documents, providing unequaled glimpses into events and personnel in the early days of rocketry that only an insider can give. His next book, Spacecraft Earth: A Guide for Passengers, is due out later in 2017. For more about Dr Richter, see his Author Profile.

Recommended Resource: Consider buying copies of The Privileged Planet in bulk to hand out at the total solar eclipse on August 21. You can obtain them in convenient quicksleeve packaging in quantities of 10, 25, 50 or 100 from for only about $3 per unit, less than a third of the usual price.


  • Bernard Goonting says:

    The Privileged Planet was an absolute joy to watch. And I look forward to the rest of Dr. Richter’s articles!

  • Fitimtari says:

    “These are regions of star building activity, where we do not want to be.” Indeed, we do not “want to be” in any belief that stars are being continuously “built” anywhere today. I doubt Dr Richter believes such a thing, and can only conclude that he wrote this by way of accommodation, i.e. looking at things from an evolutionary point of view for the sake of argument, and in order to derive a disproof-by-contradiction. Nevertheless, a clarification somewhat to this effect would have been appropriate here.

    • The “Star building” activity quote came from the Privileged Planet video. They showed Dr’s Guillermo Gonzalz and Donald Brownlee (Univ. of Washington) dwelling a little on this subject. They talked about supernovae development as well as star formation taking place in the arms of the galaxy. I guess “star building” could cover a wide variety of phenomena including decay to brown dwarfs.

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