The ancient Greeks saw the five visible planets and called them “wandering stars” because they moved randomly across the sky instead of staying in fixed positions like the stars. The word “planet” comes from the Greek word for “wanderer.”
We have known for many centuries that the planets are not stars. They appear to wander because they orbit the Sun, just like our planet Earth. They orbit at different speeds, making them appear to wander in the sky. For astronomers to classify a celestial body as a planet, it must meet three requirements:
It must have enough mass for gravity to cause it to become spherical, unlike an asteroid.
It must not have enough mass to cause thermonuclear fusion, which would make it a star.
It must have cleared the area of debris known as planetesimals.
We have five planets that are visible without the aid of telescopes or even binoculars. Two of the visible planets are called inferior planets, not because of importance but because their orbit is inside Earth’s orbit. They are Mercury and Venus. The other three are known as the superior planets since they are beyond Earth’s orbit. They are Mars, Jupiter, and Saturn.
There is one essential thing the ancient Greeks did not understand about the solar system. They did not know that it is orderly. The Greeks saw a pantheon of gods controlling various aspects of the Earth and skies. Each of their gods had all of the bad traits of humans struggling with each other. It was the Judeo-Christian concept of one almighty and wise creator God who created an orderly system that led to the scientific understanding of the cosmos.
Astronomers today use technology to examine areas of the cosmos far removed from our solar system. The fact that they are finding the other systems are very much different from ours should tell us something. In fact, the more we study those other systems, the more we learn about our solar system design and why it is the way it is.
One interesting fact about other systems is that even though some planets are very large and obviously gaseous, they can exist very close to their stars. Astronomers in the past explained the fact that the inner planets of our own solar system are rocky and hard by saying that the Sun burned off the gases and left the rocky material. That may be partially true, but in 2002 astronomers discovered a planet they named OGLE-TR-56b. It is about the same mass as Jupiter but over 30 percent larger. It has to be a gaseous planet to have such a low density.
The surprising thing is that OGLE-TR-56b orbits its star at an average distance of only 2 million miles (3.2 million km). Our innermost planet Mercury is 36 million miles (58 million km) from the Sun. The outer atmosphere of this planet must be around 3000°F (1650° C). It is evident that gaseous planets can exist very close to their stars, so our old explanation of the inner planets in our solar system design is vastly oversimplified.
Most of the planets we see around other stars are very large, which is not surprising since it is easier to see a big planet than a small one. One extra-solar planet is 17 times as massive as Jupiter. The strange thing is that many of the giant planets are closer to the Sun than Venus. Old theories of planet formation suggested that due to the large gravity values of stars, it was impossible for planets to form close to the stars. We now know that is not true.
Science programs on television have delighted in proposing that the cosmos is full of planets and that every galaxy has literally millions of planets. The hope is that if you have enough planets, the chance of having another Earth is improved. We now know that many galactic systems do not have planets at all. The composition and age of galactic systems obviously have a major impact on whether planets can exist, but claims of billions of Earth-like planets in the cosmos are highly exaggerated.
The type of star also has an impact on whether planetary systems can form. Most stars in the cosmos are binary systems containing more than one star. A planet can orbit the stars at a great distance, but shifting gravity fields make planets unlikely if the stars are close together, as most are. How much metal there is in a star system affects planet formation. Metal content varies within galaxies as well as between stars. A part of space dominated by gases like hydrogen and helium are not as likely to produce planets as areas where there are large amounts of iron, manganese, cobalt, and the like. Solar system design requires the right kind of star.
Perhaps one of the most exciting lessons we have learned from other solar systems is that the shape of the orbits of planets in our solar system is very unusual. Most of them have very circular orbits meaning that their distance from the Sun does not vary a great deal. Venus has an orbit that is .007 with 0 being a perfect circle and 1 is a straight line. Pluto has the most elliptical orbit, but even Pluto is less than .3 on the 0-1 scale. Our solar system design is unusual.
Circular orbits like ours are very rare in other solar systems where .7 is a very common orbital value, and virtually all orbits exceed .3. If a planet swings far out from its star and then comes much closer, it should be obvious that temperature conditions are going to be extreme. Not only will such a planet have extreme conditions itself, but it will have a very negative effect on any planets that do have a circular orbit in the system. If Jupiter came closer to the Sun than Earth with each orbit, imagine the conditions on Earth as Jupiter went by us.
We now know that our gas giant planets (Jupiter, Saturn, Uranus, and Neptune) are essential to us because their gravitational fields sweep up any debris from outer space. Without those planets, comets and asteroids would pound Earth and life here would be difficult if not impossible. The fact that they are outside Earth’s orbit at a considerable distance and in a circular orbit allows us to exist in a stable condition for an extended time. The comets that do enter our system by avoiding the gas giants do not come in along the plane of the solar system called the ecliptic. Coming in from other directions, they have no chance of hitting Earth since they are not in the plane of Earth’s orbit around the Sun.
For all of my life, there have been articles, videos, and public presentations claiming that there must be life elsewhere in the universe. Now that we know there are thousands of planets in the creation, we see attempts to maintain that with so many planets there must be life somewhere. Scientists are even speculating alien life without water.
We need to remember that the Bible doesn’t say that this is the only planet where God created life, so this is not a biblical issue. The latest attempts to expand the window of what life is has rejuvenated the need to show the design built into the development of life. Life on Earth is based on carbon, hydrogen, oxygen, and nitrogen. The National Science Foundation has just funded a three-year program at Saint Louis University to explore what building blocks might be used to make a different kind of life. The chemicals they are considering are hexane, ethers, and chloroform. There is particular interest in whether these materials can form membranes that could be considered life.
The first problem is the definition of life. Life has traditionally been defined as “that which can move, breathe, respond to outside stimuli and reproduce.” An extraordinary chemistry is necessary to meet all of these criteria. Water is the basic substance of life on Earth. The water molecule is polar, meaning that one end of the molecule is negative and the other end is positive. Oxygen is the negative end. Oxygen’s bonding orbitals allow the attachment of two hydrogen atoms making that end positive. This polarity allows water to dissolve other molecules. Salt, for example, is made up of sodium which is positive and chlorine which is negative. When you put salt in water, the sodium is attracted to the oxygen end of the water molecule, and the chlorine is attracted to the hydrogen end of the molecule because unlike charges attract each other. This pulls the salt molecule apart and allows the salt to dissolve. Alien life without water seems impossible.
Hydrocarbons like methane have four hydrogen atoms attached to the carbon atom symmetrically. That makes the molecule non-polar and unable to dissolve salt. Numerous experiments are underway to circumvent this problem including the use of vinyl cyanide (also called acrylonitrile) which has been found in the atmosphere of Saturn’s moonTitan. Coming up with a formula for alien life without water will be difficult. How a substitute for oxidation would work has not even been publicized, so respiration would be an equally great challenge.
When it comes to moons, it seems that Earth got cheated. We have only one moon while Mars has two. Neptune has fourteen moons. Uranus has twenty-seven. Saturn not only has rings, but it also has sixty-two moons. Lucky Jupiter has sixty-seven! To add to the embarrassment, puny little Pluto, which is no longer considered a planet, has five times as many moons as Earth has! The only bragging point we have is that we can say we have more moons than Mercury and Venus. (They have none.) So how many moons are enough?
Actually, one works very nicely. Our single moon is critical to the existence of life on Earth. It’s because of the moon that Earth has a stable tilt on its axis of 23.5 degrees. That tilt prevents temperature extremes on this planet. With no inclination, the area of the Equator would be extremely hot and the poles extremely cold and dark all year. With a greater tilt, seasonal weather changes would be extreme all over the planet. Because of the angle of the inclination, we have proper seasons, and the air gets mixed to temper the weather extremes.
Our moon has the right mass at the right distance to keep Earth’s tilt stable. The moon plays several crucial roles in making our planet a great place to live, but stabilizing the tilt is one that’s extremely important. So how many moons are enough? I would say that one moon of the right size and at the right distance is just right.
The picture shows Saturn’s moon Enceladus with Saturn in the background and part of a ring visible. Scientists are talking about a life chemical factory on Enceladus. One of the interesting questions about the origin of life is the question of how the chemicals needed to produce life came into existence.
Many believers in God answer that question just saying “God created them” and leaving it at that. For many of us with interest in science, that question expands to trying to understand HOW God created those chemicals. Saying that He spoke them into existence may be theologically acceptable, but the evidence shows that God used processes that we can understand.
Enceladus is essentially a vast ocean of water surrounded by a massive layer of ice. Scientists believe that powerful hydrothermal vents mix up the material found in the moon’s porous core with the salt water that makes up its vast ocean. This material is then ejected out into space in the form of enormous plumes of water vapor and ice granules you can see in the picture taken by the Cassini spacecraft. The sight is quite spectacular, and it was into one of these plumes that NASA’s scientists were able to send Cassini to examine their composition.
What the scientists learned is that the plumes contain organic materials. These are materials that are part of the building blocks of life. Therefore, this moon seems to be a factory that builds several of the ingredients needed to produce life.
Think of how factories produce cars. Factories at different locations all over the country build the parts. The parts come together in one place where highly skilled and creative engineers assemble them into a working automobile. In the same way, we can see a possible life chemical factory on Enceladus.
As astronomical equipment gets better, the details of stellar systems other than our own show patterns that highlight our unique solar system.
The January 3, 2018, issue of The Astronomical Journal published a report on a study of 909 planets in 355 systems discovered by the Kepler Telescope. The study shows two major patterns in neighboring exoplanets. The first is that those exoplanets tend to have similar masses. The second is that their orbits are regularly spaced from one planet to the next.
Our solar system has inner planets that have mismatched sizes, and they are widely spaced. All models of solar system formation fit what we see in exoplanets. The evidence suggests that exoplanetary systems have not been disturbed since their formation. Our system is different because it shows evidence that it has been disturbed. Jupiter and Saturn seem to be tools that modify the normal pattern of solar system formation.
In 1996 an extraterrestrial rock fragment was discovered in Egypt called the Hypatia stone. The mineral composition of that stone is unlike any other known object in our solar system. Scientists think that it originated outside of our system. Our solar system seems to be unique in both structure and chemical makeup. Astronomers are discovering indicators of how God created the Earth and all of the things that allow life to exist on it.
Yesterday we wrote about the end of the Cassini mission. We mentioned that an early highlight of that mission was landing the Huygens probe on Titan in January of 2005. Titan is a moon of Saturn and the largest moon in our solar system. Scientists were very interested in studying Titan thinking they might find evidence of life. Instead, the Titan studies verify Earth’s uniqueness.
It took seven years for the Huygens lander to make the 2.2-billion-mile (3.5 billion km) journey to Saturn on board the Cassini spacecraft. Cassini arrived at Saturn in June 2004, but it was not until Christmas Day that the Titan probe separated from the Cassini spaceship. On January 14, the probe entered the upper atmosphere of Titan at 12,400 miles (almost 20,000 km) per hour. After opening three parachutes, Huygens eventually completed a 150-minute descent to land on the surface of Titan.
As Huygens descended to the surface, it made measurements of all kinds and turned on a spotlight to photograph its soft landing. It then sent pictures and data from the surface of Titan to the Cassini spacecraft for about an hour-and-a-half. The Cassini spacecraft relayed the data and pictures to Earth. This expedition was an incredible success and told us much about conditions in another area of the solar system.
Some experts predicted that they would find life, or at least the precursors of life, on Titan. Spectrographic analysis of the atmosphere had shown a huge amount of nitrogen and some methane (natural gas) in the atmosphere. The presence of methane was of special interest to scientists because methane, with a carbon atom and four hydrogen atoms, is the building block of more complicated organic molecules. Some biochemists predicted massive numbers of complex organic molecules in oceans of hydrocarbons on Titan–perhaps even some basic life-forms.
As the Huygens probe sent back pictures from Titan, scientists were amazed to see carved river channels, old shorelines, and clouds. With a temperature of minus 300 degrees Fahrenheit (-184 C) these obviously could not be water-carved channels. As Huygens landed, it broke through a crusty surface and sank several inches into the ground. The chemical studies of the spongy surface showed that it was not rock, but frozen gaseous material. Titan’s atmosphere could not sustain life. The clouds turned out to be methane, and scientists could find no oxygen or oxygen compounds on Titan. Titan has a spongy surface saturated with organic compounds. The density of Titan tells us that deep down under all of this organic ice there must be very dense rock.
It is becoming apparent that the other planets in our solar system have very little in common with Earth. Titan studies verify Earth’s uniqueness once again. Jonathon Lunine, a planetary scientist who worked on this project, described the findings in this way, “This is a planetary scene like no other, vaguely disturbing and nightmarish to me and certainly not Mars or Venus.”
On the morning of September 15, 2017, Cassini ended its life in fiery destruction. Cassini was a space probe orbiting and studying Saturn, and by all measures, Cassini exceeded expectations.
NASA, the European Space Agency, and the Italian Space Agency worked together on the Cassini-Huygens space exploration project. The mission was to study Saturn along with its moons and rings. NASA launched the spacecraft in 1997, and it arrived near Saturn and went into orbit around that planet in 2004.
The Huygens (pronounced hoy-guns) lander module, provided by the ESA, separated from the Cassini probe and landed on Saturn’s largest moon, Titan, in 2005. The parachute landing was successful, and the probe sent out data for about 90 minutes. In that brief time, scientists learned much about the surface of that distant moon. Viewed from Titan’s surface, the Sun appeared about the size and brightness of a car headlight 150 meters away. The Huygens probe took pictures and told us that Titan’s surface is dotted with rivers, lakes, and oceans made of methane and ethane. It also has dunes up to 300 feet (91 meters) tall.
Meanwhile, the Cassini probe continued to orbit Saturn and send back amazing and beautiful pictures of its rings and moons for 13 years. Cassini helped us to learn more about the moons of Saturn. The planet has at least 53 moons and possibly eight more. We learned that the moon Enceladus is covered with a liquid water ocean with a surface layer of ice 19 to 25 miles (30 to 40 km) thick. Geysers of water erupt from cracks in the ice. The rings of Saturn are a constantly changing collection of ice particles and small rocks. Saturn has hurricane-like storms at both poles and a hexagon-shaped jet stream at the north pole. How long is a day on Saturn? That’s hard to determine because it is a gas planet and not all parts of it move at the same speed. Scientists estimate a little more than 10 hours.
Cassini exceeded expectations by surviving seven years of travel to Saturn plus 13 years orbiting the planet. As it ran out of fuel, scientists sent it hurtling into Saturn’s atmosphere to burn up so it could not contaminate any of Saturn’s moons by crashing into them.