Should We Call Pluto a Planet?

Astronomers once called Pluto the ninth planet. In 2006, the International Astronomical Union, IAU, downgraded Pluto to the status of dwarf planet. After the New Horizons craft flew by Pluto in 2015, it showed us a very dynamic world. Many astronomers and a large percentage of the public now believe we should reconsider Pluto’s demotion.

Pluto as seen by the New Horizons spacecraft. 

Since before written history, humans have known of seven regularly observed heavenly bodies that didn’t behave like the vast majority of stars. They called them planets, Greek for “wanderer.” In those ancient times, they considered anything that changed its position relative to the “fixed stars” to be a planet. Since both the sun and the Moon moved relative to the fixed stars, they were also considered planets until Copernicus proved that planets circled the sun and the Moon circled Earth.

Astronomers then recognized six planets, Mercury, Venus, Earth, Mars, Jupiter, and Saturn. Comets also orbited the sun, but because they had weird orbits and grew a tail, they were considered different types of celestial objects. That changed in 1781 when William Herschel discovered Uranus and Italian astronomer Giuseppe Piazzi discovered Ceres in 1801 between Mars and Jupiter while searching for comets. Both orbited the sun.

Ceres, the largest member of the Asteroid Belt.

Initially, astronomers called Ceres the smallest planet until many more such objects were discovered in the same area of our solar system. They reclassified Ceres and all those other even smaller objects as “asteroids,” calling that region the Asteroid Belt.

In 1846, two astronomers independently discovered Neptune, adding an 8^th planet to the solar system. Clyde Tombaugh added Pluto in 1930, making nine planets, and there it stayed for years.

In the 1990s, astronomers began finding many more objects beyond Neptune. They were small like Pluto and in the area of our solar system that was relatively crowded, unlike the inner parts. Some astronomers feared that it might be time to get a more scientifically based definition of “planet.”  

At the 2006 IAU meeting, astronomers agreed to redefine what constitutes a planet. There were two camps: geophysicists and dynamists. They all agreed that it had to orbit a star. Geophysicists said that any object big enough that its gravity pulled it into a spherical or nearly spherical shape should be a planet. Dynamists argued that a planet must also be large enough to “clear its orbital area of debris.” Ceres couldn’t be a planet since, even though it is round, there were many asteroids in the same region. Likewise, round Pluto shared its region with many thousands of objects.

The dynamists won. Pluto, Ceres, and other round solar system bodies became dwarf planets. Along with those two, astronomers now recognize three others, Haumea, Makemake, and Eris, all beyond Neptune, as dwarf planets. There may be many more that we just don’t have enough data on yet.

Count me in the camp of the geophysicists. If it’s big enough to pull itself into a nearly circular shape, technically called hydrostatic equilibrium, then I believe it should be a planet. I’m convinced that the dynamists just didn’t want to remember that many planet names.

  

    Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After publishing it there, I post that same column to my blog page.

   This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Life on Venus? New Evidence Supports the Idea

 In late 2020, a group of scientists led by Jane Greaves at Cardiff University in Wales, U.K., reported finding the gas phosphine (PH3) in the clouds of Venus. This surprised many scientists. On Earth, phosphine has two known sources: a product of microbial decay of organic material or produced in a lab. The surface of Venus bakes at nearly 900 degrees. Thick clouds of sulfuric acid surround the planet. Scientists believe such conditions completely precluded the possibility of life on Venus.

Scientists argued that the discovery must be a mistake, and other researchers who looked for phosphine in Venus’ clouds could not immediately reproduce the discovery. A March 2021 study by Rakesh Mogul of Cal Poly Pomona did find phosphine there.

Still, the controversy raged among scientists. Even if phosphine did occur in the clouds of Venus, detractors said, there must be a geochemical process that creates it that did not involve living organisms.

Venus, credit NASA

Some scientists claim that volcanoes might be a source of phosphine on Venus, which is known to have active volcanoes. Sulfur dioxide in the clouds of Venus comes from volcanoes, but as Greaves says, “The amount of phosphine doesn’t change that much across the various observations. As a comparison, sulfur dioxide, which is believed to be related to volcanism on Venus, can vary wildly, more than 10 times from year to year, or even shorter timescales.”

By comparison, the phosphine varies only by a factor or two. “It is not really variable, and I think that’s important in the context of interpretations,” said Greaves. She adds that the observations come from multiple telescopes, making the observations more robust. As Greaves said, “We now have five detections over the last few years, from three different sets of instruments, and from many methods of processing the data. We’re getting a clue here that there is some steady source (of phosphine).”

As compelling as these observations are, there is still doubt in the minds of many scientists. Follow-up studies are needed, but finding even microbial life elsewhere would be a huge discovery.

 

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

 This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Is there Life on Another World in Our Solar System?

       Life on Earth takes a bewildering, almost unimaginable range of forms. Some seem so different, it’s hard to believe they didn’t evolve on an alien planet. One resource all life on our planet requires to survive is water. Most scientists, therefore, believe that if we are to find life elsewhere, we must find a planet or moon with sufficient liquid water.

As it turns out, water is not scarce in the universe. It is a compound of atoms of hydrogen and oxygen, which are the first and third most abundant elements in the universe, making water, H2O, one of the most abundant substances in the universe.

The problem is finding water in a liquid form. On many alien planets we have discovered, the temperature is so hot that the water is all in vapor form. Or it might be underground and, perhaps, too salty to support life as we know it.

One example is Saturn’s moon Enceladus. NASA’s Cassini mission discovered jets of water spewing off the tiny moon. That really surprised scientists. They thought that moon was so small that any water would be frozen solid. But the action of Saturn’s gravity on the moon warms it up enough that Enceladus possesses a global, underground liquid water ocean. Originally, scientists assumed it might be far too salty to support life.

Water Jets spewing into space from the South Pole region of Saturn's moon Enceladus. 

Credit NASA-JPL-Space Sciences Institute

A group of researchers at MIT decided to work on a project to determine if that water could support life. They discovered that the thickness of the polar ice shell is dependent on the water’s salinity. Their analysis of data showed that the ice on the moon is thinner at the poles than at the equator. They determined that the salinity of Enceladus’ ocean is lower than that of Earth’s oceans. And Earth’s oceans contain lots of life.

Cut-away view of the ocean on Enceladus. 

Credit NASA-JPL-CalTech-Southwest Research Institute

That doesn’t automatically mean that Enceladus has life in its oceans. Other factors also determine habitability. But at least the water on the moon can support life. That dramatically increases the odds of extraterrestrial life there.

 

Each month, I write an astronomy-related column article for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.Oklahoman.com.

Oxygenating Europa's Ocean

 The only place in the entire universe that we know for certain has life is Earth. We have found tantalizing hints of possible life on Mars, Jupiter’s moon Europa, and Saturn’s moon Enceladus. A new scientific study paints an even more optimistic possibility of life on Europa.

Three essential conditions make life possible on Earth. First, life needs water. On our planet, virtually wherever water exists, so does life. Even in conditions of extreme heat, salinity, or acidity, life finds a way. Scientists have found microbes eking out a living in microscopic cracks in rock as much as three miles deep.

Secondly, life needs a source of energy. For most life on our planet, that energy source is the sun. A few organisms obtain energy from superheated water at volcanic vents on the ocean floor where sunlight never reaches. Lower life forms, like plants or microbes, use that energy to power their own life process. Other creatures feed on those plants and microbes. And, finally, life needs oxygen. Even plants, which generate the oxygen in our atmosphere must “breathe” oxygen in the absence of sunlight.

Europa, a moon of Jupiter, has numerous cracks, seen as reddish, crisscrossing lines, in a thick ice shell covering a 100-mile deep ocean. Credit NASA

Two of the most likely places in our solar system to find life beyond Earth are moons: Europa orbiting Jupiter and Enceladus which, orbits Saturn. Both possess a thick covering of ice, beneath which lie oceans of salt water. Europa’s icy shell may be as much as fifteen miles thick. The ocean that lies beneath contains more water than all of Earth’s oceans. Both are too far from the sun to power life. But both orbit large planets with strong gravitational pull. The gravity of the large planet pulls on the moons, squeezing the interior. This generates heat in the core that moves up into the oceans. Without this heating, both moons would be solid ice. For Europa, oxygen exists on the surface. Getting it through the thick ice shell is the problem.

A new study led by researcher Marc Hesse, of the UT Jackson School of Geosciences, suggests a solution. Europa’s surface is covered with cracks. And the pulling, squeezing action of Jupiter’s gravity can pump surface brine with dissolved oxygen through these cracks to the ocean below. They estimate that 86% of the oxygen on Europa’s surface can reach the ocean through this process, allowing Europa’s ocean to carry as much oxygen as Earth’s oceans. "It provides a solution to what is considered one of the outstanding problems of the habitability of the Europa subsurface ocean," Hesse says.

  

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted with permission from the Oklahoman and www.Oklahoman.com.

Is the Hypothesized "Planet Nine" Actually a Primordial Black Hole?

 On March 13, 1781, astronomer William Herschel pointed his telescope into the night sky and discovered the planet Uranus, the first such discovery in historical times. Over the next 45 years, as astronomers observed Uranus looking for possible moons, they realized its orbit didn’t follow the known laws of gravity. Some astronomers surmised that perhaps Newton’s gravitational laws didn’t work so far from the sun.

But two mathematicians decided that the discrepancy occurred due to the gravitational attraction of an eighth planet even farther out. Unbeknownst to each other, both French astronomer Rubin Le Perrier and British mathematician John Couch Adams began calculating the likely position of such a planet based on the aberrations of the orbit of Uranus. On September 23, 1846, French astronomer Johanne Galle found Neptune within one degree of the predicted position. The effect of Neptune’s gravitational pull on the orbit of Uranus led to its discovery.

In January 2015, Caltech astronomers Konstantin Batygin and Mike Brown noted some rather odd orbits of five asteroids in the far outer regions of our solar system. Using computer modeling, they predicted the presence of a ninth planet ten times larger than Earth whose gravity they theorized affected the asteroids. They dubbed it “Planet Nine.”

That planet has never been discovered even with today’s sophisticated telescopes, yet according to Brown and Batygin, new evidence continues to support their hypothesis. This negative result has led some astronomers to propose a radical idea: maybe the cause of the odd orbits isn’t a large planet but rather a small black hole.

Typically, black holes result from the death of massive stars and are typically five to ten times the mass of our sun. But the extreme conditions at the earliest stages of the formation of the universe could have created smaller, planet-sized black holes, called primordial black holes, although we’ve yet to find any. 

Primordial black holes may exist throughout the cosmos. Credit NASA

A planet ten times the size of Earth should have been found, many astronomers believe, but a black hole of the same mass would be tiny and impossible to see. The only way to discover one is to use the same method astronomers use to find any stellar-sized black hole, by way of its massive gravity. A planet-sized black hole might be invisible, but the gravity of one could certainly cause the observed effect.

I think the idea of a primordial black hole at the edge of our solar system is exciting. As long as it stays out there.

Life Below Earths Ocean Floor Give Scientists Hope for Finding Life on Mars

Ten years ago, scientists from the University of Tokyo, Japan, led an expedition to drill into rock 400 feet below the ocean floor. They have been studying the various rock samples, ranging in age from thirteen million years to 104 million years, ever since. Theses ocean rocks formed when undersea volcanoes spewed out lava which cooled into fractured rock and became buried under ocean sediment. The cracks filled with clays from the ocean floor.

The scientists knew that rocks beneath the surface of dry land were home to bacteria, and they looked for bacteria living in the ocean rocks. After intense study, with some missteps along the way, they finally found dense bacterial colonies, numbering more than 100 billion bacterial cells per cubic inch, living in the clay-filled cracks. This density of bacteria is similar to that found in the human gut. That compares to a paltry 1000 bacteria per cubic inch living in the muddy layers above the rock on the ocean floor.

"I thought it was a dream, seeing such rich microbial life in rocks," said Associate Professor Yohey Suzuki from the University of Tokyo, one of the leaders of the expedition. "Honestly, it was a very unexpected discovery. I was very lucky because I almost gave up."

This finding excites astrobiologists who search for signs of past, or present, life on Mars. Much of Mars was once covered by lakes and oceans, with similar clay minerals. Just as in the Earth study, Martian ocean sediments were eventually covered and compressed into rock at the bottom of those bodies of water.

"Minerals are like a fingerprint for what conditions were present when the clay formed. Neutral to slightly alkaline levels, low temperature, moderate salinity, iron-rich environment, basalt rock -- all of these conditions are shared between the deep ocean and the surface of Mars," said Suzuki.

Mars 2020 Rover Perseverance. Credit NASA

NASA will launch the next Martian rover, Perseverance, in late July or early August. Among other scientific instruments, Perseverance posses a biological testing lab that will search for similar bacterial colonies, living or fossilized, in similar Martian rock that was once the bottom of a Martian sea. The findings of Dr. Suzuki’s team gave NASA scientists the road map for searching for ancient, Martian bacterial colonies that may, perhaps, tell us that Mars was once, possibly still is, a home for life.

 Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and www.newsok.com.

A Second Moon

In the late 1960s and early 1970s, NASA astronauts brought 842 pounds of rock and soil from the Moon to Earth. In addition to those samples, scientists have found more than 370 meteorites known to have come from the Moon, weighing a total of 489 pounds.

That’s impressive, but what if astronauts could bring the entire moon back to Earth?

Not that Moon. The other one.

On February 15^th, astronomers with the NASA-funded Catalina Sky Survey at the University of Arizona announced the discovery of a new moon orbiting Earth. Kacper Wierzchos, one of the astronomers who made the discovery, posted several images of the object, designated 2020 CD3. Analysis of its orbit indicated that Earth’s gravity captured it three years ago when it was a small asteroid orbiting the sun. It’s tiny, only 6 to 12 feet in diameter. While it is too small to see without a large telescope, it is also small enough to be captured in a ship and returned to Earth. It is a captured asteroid and studying its makeup goes a long way to helping us better understand the origin of our solar system.

2020 CD3 Image credit: Kacper Wierzchos, Catalina Sky Survey, NASA

Wierzchos said of the discovery “It's a big deal, as out of approximately one million known asteroids, this is just the second asteroid known to orbit Earth (after 2006 RH120, which was also discovered by the Catalina Sky Survey).”

2006 RH120 eventually left Earth orbit after only nine months due to gravitational tugs and radiation pressure from the sun. 2020 CD3 will likely also leave Earth orbit eventually, but there is currently no evidence that solar radiation pressure is affecting its orbit. And it has already been a second moon for three years. So perhaps it will stick around for a while.

The Catalina Sky Survey’s mission is to hunt for and catalog all near-Earth asteroids that may pose an impact risk to Earth. While 2020 CD3 would not be a significant risk to Earth on impact, due to its small size, discovering that it is now Earth’s second moon may be even more exciting.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and www.newsok.com.

Help Find the Next Asteroid Threat to Earth

According to NASA’s Asteroid Fast Facts page, a lot of space material lands on Earth every year. From the NASA page:

“Every day, Earth is bombarded with more than 100 tons of dust and sand-sized particles.

“About once a year, an automobile-sized asteroid hits Earth's atmosphere, creates an impressive fireball and burns up before reaching the surface.

Every 2,000 years or so, a meteoroid the size of a football field hits Earth and causes significant damage to the area.”

Image Credit NASA

When is the next one coming? No one knows. But NASA and other organizations worldwide constantly watch out for possible impactors from space. Even so, some escape discovery until they hit. In 2013, a small asteroid, about the size of a six-story building, entered our atmosphere over Chelyabinsk, Russian. It exploded with a blast more powerful than the atomic bomb over Hiroshima. The blast shattered glass in buildings all over the city and caused injuries to more than 1,200 people. It was so bright that scientists estimate it briefly outshone the sun. We had no warning of this event. No one saw it coming.

Many telescopes automatically search the night sky for incoming asteroids, for one with Earth in its sights. But scientists need your help finding them. You may be the one to spot the next one that threatens Earth.

Image Credit NASA

An organization called Zooniverse (https://www.zooniverse.org/projects) currently has 108 projects where anyone, even you, can help scientists make new discoveries. I have written about Zooniverse before, but they have added quite a few new projects since then and more are added every year. You can find them at www.zooniverse.org.

The project to help find potentially dangerous asteroid is at www.zooniverse.org/projects/sandorkruk/hubble-asteroid-hunter. As with all the Zooniverse projects, you get a brief tutorial on what to look for and how to identify a target. Then you are presented with a series of photos. Using what you learned in the tutorial, you identify potential asteroid targets. Once identified, the project scientists analyze the photo to calculate the asteroid’s path to determine if Earth is in the way.

If saving the Earth from asteroid impacts isn’t your cup of tea, look through all of their projects. It’s likely one or several of the others will pique your interest.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and https://oklahoman.com/.

Measurements Give New Insight into the Structure of the Lunar Crust

Everyone has seen the full Moon in the night sky. The familiar dark splotches called ‘maria,’ Latin for seas, create patterns on the lunar surface. Some people see a man’s face, the Man in the Moon. Others imagine a frog or a rabbit. Whatever you might picture when you look at the full Moon, the pattern of large, dark areas overlying lighter material is quite obvious. The maria are composed of lava that poured out from asteroid impacts and covered the lighter surface material.

The Lunar Nearside, credit NASA

From Earth, we only see the one side of the Moon, so you might assume this arrangement of maria over lighter material continues on the far side of the Moon. Astronomers assumed that, too, until the Russian Luna 3 spacecraft sent back the first, grainy pictures of the lunar far side in 1959. Although there were a few dark patches, they were quite a bit smaller than the familiar maria of the near side and didn’t cover much of the far side surface.

The Lunar Farside, credit NASA

Subsequent studies of the Moon revealed that the crust on the far side is as much as 10 miles (ca. 16 km) thicker than the near side crust. Because of this, asteroids can’t so easily puncture the far side crust, so fewer and smaller maria formed there. For decades, astronomers puzzled as to what might have caused this. Until recently, the best idea was that we originally had two moons. Very early on, the two collided at low speed on the far side. The material from the smaller impacting moon flowed over that side, creating the thicker crust.

Measurements made by the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012 provided more data, suggesting an impact from an outsider. "The detailed gravity data obtained by GRAIL has given new insight into the structure of the lunar crust underneath the surface," said Meng Hua Zhu, a co-author on the new paper on the subject and a scientist at Macau University of Science and Technology in China. Using computers, the researchers modeled 360 different collisions and compared all the results to what we know about the moon today. The best fit with our Moon suggests that a collision of an object 500-560 miles (ca. 805-901 km) across could have done the trick.

Artists concept of Lunar Farside collision, credit NASA

Luckily for us, there are no other such large objects wandering around near our orbit today.

On or about the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and www.newsok.com.

Water on Mars from Deep Groundwater Sources

In 2015, NASA announced the discovery of water flowing down the sides of craters on Mars. NASA calls them Reoccurring Slope Lineae, RSL for short. This seemed to answer the question of whether liquid water currently existed on Mars. And since liquid water is believed to be a prime requirement for life, the discovery also reinvigorated the discussion of life, even if only microscopic, on the red planet. You can see a NASA video montage of some RSLs at https://youtu.be/H44-XrGH5IQ.

Reoccurring Slope Lineae on Mars, credit NASA

In 2017, some researchers published papers suggesting RSLs were not from water but consisted of sand sliding down the slopes, driven by carbon dioxide that sublimated from dry ice just below the surface. Carbon dioxide, being a relatively heavy gas, flows downhill and carries sand grains with it. The researchers suggested that the sand just below the surface might be darker, having not been bleached by UV radiation from the sun.

The consensus of scientific opinion, however, rested with water flow, but many wondered if water just below the surface of the cold planet could never melt. Recently, Essam Heggy, a research scientist at the University of Southern California and NASA's Jet Propulsion Laboratory, and Abotalib Z. Abotalib, a postdoctoral research associate at USC, suggested that the flows are triggered not by near-surface water but rather from deep below the surface. "We propose an alternative hypothesis, that they originate from a deep, pressurized groundwater source, which comes to the surface, moving upward along ground cracks," said Hegggy.

They compared Martian geological features to similar ones on Earth and determined that heat flow in the Martian subsurface was similar to that in desert regions here on Earth. This research, the two concluded, indicates that RSL water is probably coming from deeply buried, briny aquifers.

This even explains the seasonal aspect of the flows. "The system shuts down during winter seasons, when the ascending near-surface water freezes within fault pathways, and resumes during summer seasons when brine temperatures rise above the freezing point," the researchers wrote.

The new study says nothing about the existence of life on Mars, but it will surely strengthen arguments for at least microbial Martians living below the surface.

       On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

      This is reprinted by permission form the Oklahoman and www.newsok.com.