Are We Close to Finding Earth 2?

 

NASA and other space agencies have launched several missions to search for exoplanets, planets that orbit other stars. The Holy Grail of such programs is finding an Earth-like planet orbiting a sun-like star at the right distance to allow liquid water on the surface. Such planets seem to be the most likely candidates to search for life.

While astronomers have yet to find a perfect Earth 2, statistical analysis of NASA’s most successful planet hunter, the Kepler Mission, uncovered some promising data. A study by NASA scientists alongside collaborators from around the world who worked on the Kepler mission came to an exciting conclusion. According to the research, about half the stars similar in temperature to our Sun could have a rocky planet capable of supporting liquid water on its surface.

Image Caption/Credit: NASA’s Kepler Planet Finder telescope, credit NASA

"Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable," said the lead author Steve Bryson, a researcher at NASA's Ames Research. "Though this result is far from a final value, and water on a planet's surface is only one of many factors to support life, it's extremely exciting that we calculated these worlds are this common with such high confidence and precision."

Kepler detected planets by continuously staring at thousands of stars, watching for a tell-tale drop in brightness caused by an orbiting planet crossing in front of a star. Such a method couldn’t detect planetary systems seen more face on, so astronomers had to use statistical methods to extrapolate from the Kepler data to all the other stars in our galaxy. Kepler discovered so many exoplanets from its limited mission that astronomers now believe that more than half of the four billion stars in the Milky planet possess planets, typically more than one.

Using their most conservative estimate, that 7% of all sun-like stars have Earth-like planets, meaning some 300 million exist in our Milky Way alone. Their most likely estimate states that Earth-like planets orbit 50% of sun-like stars, making more than 2 billion Earth-like planets. Since we know of only one planet with life, ours, those planets are the best place to begin to search for alien forms of 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.

Where Did the Gold in Your Ring Come From?

 

Astronomers have a pretty good understanding of where the matter in our universe comes from. In the beginning, there was only hydrogen, helium, and a tiny smattering of lithium. Everything else, the oxygen we breathe, the carbon that makes up so much of our bodies, the silicon, magnesium, aluminum, and other elements that make up our planet, were all formed inside stars and released into the wider universe when stars explode.

Supernova Remnent Casseopeia A. Credit NASA

But there is one element that still has astronomers bumfuzzled: gold. There is too much of it. Supernova explosions can’t begin to account for the amount that we see because the gold is trapped in the neutron stars, the remnants of supernovas. Colliding neutron stars release prodigious amounts of gold, as do so-called magneto-rotational supernova. These rare supernovas spin so fast and generate such strong magnetic fields that they literally turn themselves inside out. This releases all of their trapped gold atoms. But while both produce extraordinary quantities of gold, they are extremely rare and cannot begin to account for all the gold we find here on Earth.

Chiaki Kobayashi is an astrophysicist at the University of Hertfordshire in the United Kingdom. She led the new study to determine the origin of gold. "There are two stages to this question," she said. "Number one: neutron star mergers are not enough. Number two: Even with the second source, magneto-rotational supernova, we still can't explain the observed amount of gold." Kobayashi and the other study authors accounted for the formation and relative abundance of all elements from carbon to uranium. All except for gold. Its abundance remains a mystery.

So, the next time you put on that gold ring or necklace, you can marvel that our Earth has as much gold as it does.

 

 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.

 

Martian Life, if it Exists, Could Still Be Present Underground

 

Earth sits right in the middle of our sun’s habitable zone, the region where the heat of the star allows liquid water to exist on the surface of a planet. Mars orbits at the outer edge of this zone. Astronomers generally agree that Mars once sported rivers, lakes and, oceans. Mars reached such life-supporting conditions even before Earth. Its smaller size allowed it to cool more quickly from the heat of formation.

But Mars’ smaller size also allowed its core to cool and solidify long ago, killing its magnetic field. Without that magnetic field, solar radiation slowly knocked the atmosphere of Mars into space. Lacking an atmosphere, Mars couldn’t trap the sun’s heat, so it turned cold. Nighttime temperatures routinely drop to near 100 degrees below zero.

But, prior to the loss of its atmosphere, Mars sported conditions that could have supported life. That is no longer true of the surface of Mars. The thin atmosphere can no longer warm the surface of Mars nor protect it from cosmic radiation. Many scientists, including astrophysicist and research scientist Dimitra Atri, from the Center for Space Science at NYU Abu Dhabi, believe that conditions not far below the surface could potentially support life, albeit only at the bacterial level.

In 2022, the European Space Agency and Roscosmos, the Russian space organization, will launch the ExoMars craft, which includes the Rosiland Franklin rover. Atri says that rover will have the ability to detect any such subsurface life on the Red Planet. "It is exciting to contemplate that life could survive in such a harsh environment, as few as two meters (six feet) below the surface of Mars," said Atri. "When the Rosalind Franklin rover onboard the ExoMars mission, equipped with a subsurface drill, is launched in 2022, it will be well-suited to detect extant microbial life."

                           ExoMars Rosalind Franklin rover, Credit European Space Agency (ESA).

If we find life on Mars, it will indicate that life forms easily, given that life developed on both planets in our solar system capable of supporting it. That tells astronomers that perhaps many of the tens of billions of Earth-like planets in our Milky Way galaxy likely did, too.

     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.