Scientists do not know what is causing the overabundance of the gas.
- A new study looked to understand the source of methane on Saturn's moon Enceladus.
- The scientists used computer models with data from the Cassini spacecraft.
- The explanation could lie in alien organisms or non-biological processes.
Something is producing an overabundance of methane in the ocean hidden under the ice of Saturn's moon Enceladus. A new study analyzed if the source could be an alien life form or some other explanation.
The study, published in Nature Astronomy, was carried out by scientists at the University of Arizona and Paris Sciences & Lettres University, who looked at composition data from the water plumes erupting on Enceladus.
The particular chemistry, discovered by the Cassini spacecraft which flew through the plumes, suggested a high concentration of molecules that have been linked to hydrothermal vents on the bottom of Earth's oceans. Such vents are potential cradles of life on Earth, according to previous studies. The data from Cassini, which has been studying Saturn after entering its orbit in 2004, revealed the presence of molecular hydrogen (dihydrogen), methane, and carbon dioxide, with the amount of methane presenting a particular interest to the scientists."We wanted to know: Could Earthlike microbes that 'eat' the dihydrogen and produce methane explain the surprisingly large amount of methane detected by Cassini?" shared one of the study's lead authors Régis Ferrière, an associate professor in the department of Ecology and Evolutionary Biology at the University of Arizona.
Earth's hydrothermal vents feature microorganisms that use dihydrogen for energy, creating methane from carbon dioxide via the process of methanogenesis.
Searching for such microorganisms known as methanogens on the seafloor of Enceladus is not yet feasible. Likely, it would require very sophisticated deep diving operations that will be the objective of future missions.
So, Ferrière's team took a more available approach to pinpointing the origins of the methane, creating mathematical models that attempted to explain the Cassini data. They wanted to calculate the likelihood that particular processes were responsible for producing the amount of methane observed. For example, is the methane more likely the result of biological or non-biological processes?
They found that the data from Cassini was consistent with either microbial activity at hydrothermal vents or processes that have nothing to do with life but could be quite different from what happens on Earth. Intriguingly, models that didn't involve biological entities didn't seem to produce enough of the gas.
"Obviously, we are not concluding that life exists in Enceladus' ocean," Ferrière stated. "Rather, we wanted to understand how likely it would be that Enceladus' hydrothermal vents could be habitable to Earthlike microorganisms. Very likely, the Cassini data tell us, according to our models."
Still, the scientists think future missions are necessary to either prove or discard the "life hypothesis." One explanation for the methane that does not involve biological organisms is that the gas is the result of a chemical breakdown of primordial organic matter within Enceladus' core. This matter could have become a part of Saturn's moon from comets rich in organic materials.
Tiny fluctuations in old Kepler data reveals four runaway planets that are reminiscent of Earth.
- Scientists discover four rogue planets that are unbound to any star.
- The discovery was made thanks to tiny microlensing light curves in data from the retired Kepler telescope.
- There may be billions of such rogue planets in our galaxy.
It's a familiar model: a solar system comprised of several planets orbiting a sun. And it's mostly true. However, it's not always true. A study just published in the Monthly Notices of the Royal Astronomical Society announces the discovery of four Earth-sized planets roaming freely through the universe on their own.
One last victory for Kepler
The find is a late-life triumph for the aging Kepler Telescope, which was retired in October 2018. Evidence for the planets appears in data from its K2 data collection mission that began when the craft's four gyroscope wheels, which allowed scientists to point Kepler at specific objects, failed in 2013.
"Our observations pointed an elderly, ailing telescope with blurred vision at one of the most densely crowded parts of the sky," says lead author of the study Iain McDonald of the University of Manchester, "where there are already thousands of bright stars that vary in brightness, and thousands of asteroids that skim across our field."
The K2 missions consisted of a series of campaigns in which the space telescope could observe star fields visible from the Earth's ecliptic plane as it orbited the planet. During these campaigns, mission controllers were able to keep Kepler in position by firing its thrusters and using its remaining pair of wheels. Each campaign lasted 80 days, after which the sun's angle changed and solar winds disrupted control of Kepler's attitude — that is, its angular orientation.
General relativity and microlensing
Kepler was originally designed to detect exoplanets using the "transit method" that looks for dips in the brightness of celestial objects (such as stars) as other objects (such as planets) pass in front of them. The craft detected thousands of exoplanets during its primary mission. However, this method only works for planets orbiting stars, and the Royal Academy astronomers were interested in looking for rogue planets.
Enter microlensing. Albert Einstein predicted 85 years ago that general relativity would allow objects to be seen due to microlensing, an effect that increases a distant object's brightness as nearby objects pass in front of it. This brief magnification effect could last anywhere from hours to a few days. These signals might be so subtle, says co-author Eamonn Kerins of the University of Manchester, that "Einstein himself thought that they were unlikely ever to be observed."
Poring through 2016 K2 data, the study's authors identified 27 short-duration microlensing candidates in the crowded star field, most of which were confirmed by observations from other systems. Four, however, were brand-new discoveries. Their super-brief durations suggest four lonely objects approximating the Earth in mass floating through space.
It is not yet known what would cause a planet to break free from its star, though it has been theorized that the gravitational pull of large nearby objects may yank them from the grasp of their solar system.
Still, rogue planets may not be uncommon. NASA says there may be twice as many free-floating Jupiter-mass planets as stars. Astronomers from the University of Leiden in the Netherlands say there are likely to be billions of rogue planets careening through the Milky Way. And astronomer Simon Portegies Zwart proposes that even our own solar system may have lost a Neptune-sized planet long ago.
Most planets can't host plant life.
- A new study examines if exoplanets get enough stellar radiation to support photosynthesis.
- Many planets within the habitable zones of stars do not receive enough energy to support plant life.
- Earth-like planets are probably very rare.
Since 1961, astrobiologists and others interested in finding extraterrestrial life have used the Drake equation to speculate on the possible number of technologically advanced alien civilizations in the Milky Way. By multiplying factors like the number of new stars in the galaxy per year, how many planets those stars have, the number of planets suited to life, and how long intelligent civilizations emit radio waves, one can get an estimate of how many other intelligent species are out there right now.
The problem is that the equation is almost entirely speculative because many of the factors have unknown values. But every once in a while, new information helps to narrow down the range of reasonable values to plug in.
Bad news for E.T. enthusiasts: a new study published in Monthly Notices of the Royal Astronomical Society offers a further narrowing of those values. By examining the conditions needed for photosynthesis, the authors propose that biospheres suitable for life might be rarer than we thought.
Let there be (a little more) light
The study's authors looked at what conditions are needed for the biochemical process that makes most life on Earth possible, oxygenic photosynthesis. By combining carbon dioxide with water and light, species capable of oxygenic photosynthesis produce sugar and oxygen. The latter is released as a waste product.
The authors, like many before them, conjecture that photosynthesis is common throughout the galaxy on account of how much stellar radiation there is to collect, the (comparative) simplicity of the process, and the abundance of the other input elements.
Unlike others before them, they set out to see if any known exoplanets in the habitable zones of their stars actually got enough photosynthetically active radiation (PAR) — a term for solar radiation in the wavelength range between about 400 and 700 nm that most plants can use — to support life. By analyzing how much PAR known exoplanets are getting from their stars, the researchers were able to estimate which of them are getting enough stellar energy to have an Earth-like biosphere filled with photosynthesizing plants.
As it turns out, good real estate is hard to come by in the Milky Way.
Stars that burn at half the heat of the sun do not provide enough energy for a rich biosphere to ever arise. Red dwarf stars, which are small, numerous, and burn at about a third of the sun's temperature, were even worse. They couldn't provide the energy needed for much photosynthesis at all.
"Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope. This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the 'sweet spot' for hosting a rich Earth-like biosphere is not so wide."
On the other end of the scale, very large and bright stars do produce enough light to drive photosynthesis. However, these stars also run out of fuel and either burn out or explode before advanced life would have a chance to evolve.
The Rare Earth hypothesis
This doesn't mean that we are alone in the universe. While the study does suggest that the number of planets suitable for life is lower than we thought, the number is not impossibly small. The authors mention the existence of some planets, such as Kepler-442b, which do get enough solar radiation to sustain an Earth-like biosphere.
The study supports the argument known as the "Rare Earth hypothesis." It is, as the name suggests, the idea that planets like Earth — that is, planets that have the right combination of factors for complex life to evolve — are comparatively rare in the cosmos. (Those who object claim that life could evolve in ways unknown on Earth.)
The hunt will continue for alien life. Just don't get your hopes up.
The Taupo volcano was responsible for one of the most violent eruptions on record.
- The Taupo volcano is a rhyolitic supervolcano, whose caldera is filled by the largest freshwater lake in New Zealand.
- About 26,500 years ago, the Taupo volcano generated the Ōruanui eruption, one of the most violent on record.
- A recent study found that the Taupo volcano was likely responsible for increased seismic activity in nearby areas, suggesting the need for increased monitoring.
From the shores of Lake Taupo, a large freshwater lake in the center of New Zealand's North Island, visitors would have a hard time discerning the geological anomaly lurking below the surface: the Taupo volcano.
Around 26,500 years ago, the supervolcano produced one of the most powerful eruptions in geological history, spewing 750 cubic miles of ash and pumice into the air, covering far-away islands with inches of ash and forever changing the topography of the nation. The Ōruanui eruption was so strong that the volcano collapsed in on itself, forming a 360-foot-deep caldera that's now mostly filled by Lake Taupo.
The Taupo volcano has since remained active. It last erupted about 1,800 years ago, filling nearby valleys with so much ignimbrite that the valleys were leveled out. But like all volcanoes, its activity isn't limited to magmatic eruptions; it also includes earthquakes and ground deformation, which can occur without eruptions.
A study recently published in the journal Geochemistry, Geophysics, Geosystems found that the Taupo volcano underwent a period of unusually high volcanic unrest in 2019. The results don't suggest a supereruption will occur anytime soon, but it's possible that the Taupo volcano system could produce smaller eruptions in the near future, highlighting the need for improved monitoring techniques.
Taupō supervolcano and caldera – Ōruanui eruption, 25,500 years ago www.youtube.com
Volcanic unrest on North Island
It was no secret that powerful underground processes have been at work on New Zealand's North Island. After all, the region near the Taupo volcano was struck by more than 750 earthquakes in 2019 alone. But it wasn't immediately obvious that those earthquakes were caused by the sprawling volcano system; local tectonic processes unrelated to the magmatic system could have caused the quakes.
To determine the cause of the unrest, the researchers behind the new study analyzed data on the time, location, and magnitudes of recent earthquakes on North Island. The analysis showed that the likely cause of the 2019 earthquake "swarms" was an inflating magma reservoir about 3.1 miles below ground.
"This inflation was contemporaneous with the earthquake activity that was occurring at both the NE and SW edges of the broader magma reservoir," the researchers wrote. "We suggest that the reason for this seismicity distribution is that in the aseismic region below the Horomatangi Reefs the brittle-ductile transition is very shallow due to the presence of a large magma reservoir."
Will Taupo erupt soon?
Because volcanic activity can signal imminent eruptions, the researchers noted that New Zealand officials probably should have issued an alert for "minor volcanic unrest." However, they acknowledged that it would have been difficult for officials to determine the cause of the earthquakes in real time. After all, it's not easy to monitor volcanoes, especially Taupo, much of which lies under a 238-square-mile lake. It's even harder to forecast eruptions. One key reason is that volcanic unrest always precedes eruptions, but eruptions don't always follow volcanic activity.
Since the Ōruanui eruption, the Taupo volcano has erupted at least 28 times, the most powerful of which was the eruption that occurred around the year 232. What are the chances of Taupo erupting with similar force in our lifetimes? Not great. A 2020 paper published in Earth and Planetary Science Letters put the annual odds of such an eruption occurring over the next 500 years between 0.5 and 1.3 percent. Magma needs more time to accumulate before a super-eruption is likely.
Still, volcanic eruptions worldwide have killed about 2,000 people since 2000, 22 of whom died when a stratovolcano on New Zealand's White Island erupted in 2019. The researchers behind the new study said their findings highlight the need for improved monitoring techniques.
"Our findings show that Taupo needs to be carefully monitored to better understand the processes at depth and the factors that might cause similar unrest to escalate into an eruption in the future," the researchers wrote.
Geologists discover a rhythm to major geologic events.
- It appears that Earth has a geologic "pulse," with clusters of major events occurring every 27.5 million years.
- Working with the most accurate dating methods available, the authors of the study constructed a new history of the last 260 million years.
- Exactly why these cycles occur remains unknown, but there are some interesting theories.
Our hearts beat at a resting rate of 60 to 100 beats per minute. Lots of other things pulse, too. The colors we see and the pitches we hear, for example, are due to the different wave frequencies ("pulses") of light and sound waves.
Now, a study in the journal Geoscience Frontiers finds that Earth itself has a pulse, with one "beat" every 27.5 million years. That's the rate at which major geological events have been occurring as far back as geologists can tell.
A planetary calendar has 10 dates in red
Credit: Jagoush / Adobe Stock
According to lead author and geologist Michael Rampino of New York University's Department of Biology, "Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random."
The new study is not the first time that there's been a suggestion of a planetary geologic cycle, but it's only with recent refinements in radioisotopic dating techniques that there's evidence supporting the theory. The authors of the study collected the latest, best dating for 89 known geologic events over the last 260 million years:
- 29 sea level fluctuations
- 12 marine extinctions
- 9 land-based extinctions
- 10 periods of low ocean oxygenation
- 13 gigantic flood basalt volcanic eruptions
- 8 changes in the rate of seafloor spread
- 8 times there were global pulsations in interplate magmatism
The dates provided the scientists a new timetable of Earth's geologic history.
Tick, tick, boom
Credit: New York University
Putting all the events together, the scientists performed a series of statistical analyses that revealed that events tend to cluster around 10 different dates, with peak activity occurring every 27.5 million years. Between the ten busy periods, the number of events dropped sharply, approaching zero.
Perhaps the most fascinating question that remains unanswered for now is exactly why this is happening. The authors of the study suggest two possibilities:
"The correlations and cyclicity seen in the geologic episodes may be entirely a function of global internal Earth dynamics affecting global tectonics and climate, but similar cycles in the Earth's orbit in the Solar System and in the Galaxy might be pacing these events. Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists."
Assuming the researchers' calculations are at least roughly correct — the authors note that different statistical formulas may result in further refinement of their conclusions — there's no need to worry that we're about to be thumped by another planetary heartbeat. The last occurred some seven million years ago, meaning the next won't happen for about another 20 million years.