Intense Storms Batter Saturn’s Largest Moon, Scientists Report

Titan, the largest of Saturn’s more than 60 moons, has surprisingly intense rainstorms, according to research by a team of UCLA planetary scientists and geologists. Although the storms are relatively rare — they occur less than once per Titan year, which is 29 and a half Earth years — they occur much more frequently than the scientists expected.

“I would have thought these would be once-a-millennium events, if even that,” said Jonathan Mitchell, UCLA associate professor of planetary science and a senior author of the research, which was published Oct. 9 in the journal Nature Geoscience. “So this is quite a surprise.”

The storms create massive floods in terrain that are otherwise deserts. Titan’s surface is strikingly similar to Earth’s, with flowing rivers that spill into great lakes and seas, and the moon has storm clouds that bring seasonal, monsoon-like downpours, Mitchell said. But Titan’s precipitation is liquid methane, not water.

“The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer,” said Mitchell, the principal investigator of UCLA’s Titan climate modeling research group.

Sean Faulk, a UCLA graduate student and the study’s lead author said the study also found that the extreme methane rainstorms may imprint the moon’s icy surface in much the same way that extreme rainstorms shape Earth’s rocky surface.

On Earth, intense storms can trigger large flows of sediment that spread into low lands and form cone-shaped features called alluvial fans. In the new study, the UCLA scientists found that regional patterns of extreme rainfall on Titan are correlated with recent detections of alluvial fans, suggesting that they were formed by intense rainstorms.

The finding demonstrates the role of extreme precipitation in shaping Titan’s surface, said Seulgi Moon, UCLA assistant professor of geomorphology and a co-senior author of the paper. Moon said the principle likely applies to Mars, which has large alluvial fans of its own, and to other planetary bodies. Greater understanding of the relationship between precipitation and the planetary surfaces could lead to new insights about the impact of climate change on Earth and other planets.

Titan’s alluvial fans were detected by a radar instrument on the Cassini spacecraft, which began orbiting Saturn in late 2004. The Cassini mission ended in September 2017, when NASA programmed it to plunge into the planet’s atmosphere as a way to safely destroy the spacecraft.

Juan Lora, a UCLA postdoctoral scholar and a co-author of the paper, said Cassini has revolutionized scientists’ understanding of Titan.

Although Titan’s alluvial fans are a new discovery, scientists have had eyes on the moon’s surface for years. Shortly after Cassini reached Saturn, radar and other instruments showed that vast sand dunes dominated Titan’s lower latitudes, while lakes and seas dominated its higher latitudes. The UCLA scientists found that the alluvial fans are mostly located between 50 and 80 degrees latitude — close to the centers of the moon’s northern and southern hemispheres, but generally slightly closer to the poles than to the equator.

Such variations in surface features suggest the moon has corresponding regional variations in precipitation, because rainfall and subsequent runoff play a key role in eroding land and filling lakes, while the absence of rainfall promotes the formation of dunes.

Previous models have shown that liquid methane generally concentrates on Titan’s surface at higher latitudes. But no previous study had investigated the behavior of extreme rainfall events that might be capable of triggering major sediment transport and erosion, or shown their connection to surface observations.

The scientists primarily used computer simulations to study Titan’s hydrologic cycle because observations of actual precipitation on Titan are difficult to obtain and because, given the length of each year on Titan, Cassini only observed the moon for three seasons. They found that while rain mostly accumulates near the poles, where Titan’s major lakes and seas are located, the most intense rainstorms occur near 60 degrees latitude — precisely the region where alluvial fans are most heavily concentrated.

The study suggests that the intense storms develop due to the sharp differences between the wetter, cooler weather in the higher latitudes and the drier, warmer conditions in the lower latitudes. Similar temperature contrasts on Earth produce intense cyclones in the mid-latitudes, which is what creates the storms and blizzards that are common during the winter months across much of North America.

The research was funded by a NASA Cassini Data Analysis and Participating Scientists Program grant.

Giant Exoplanet Hunters: Look For Debris Disks

There’s no map showing all the billions of exoplanets hiding in our galaxy — they’re so distant and faint compared to their stars, it’s hard to find them. Now, astronomers hunting for new worlds have established a possible signpost for giant exoplanets.

A new study finds that giant exoplanets that orbit far from their stars are more likely to be found around young stars that have a disk of dust and debris than those without disks. The study, published in The Astronomical Journal, focused on planets more than five times the mass of Jupiter. This study is the largest to date of stars with dusty debris disks, and has found the best evidence yet that giant planets are responsible for keeping that material in check.

“Our research is important for how future missions will plan which stars to observe,” said Tiffany Meshkat, lead author and assistant research scientist at IPAC/Caltech in Pasadena, California. Meshkat worked on this study as a postdoctoral researcher at NASA’s Jet Propulsion Laboratory in Pasadena. “Many planets that have been found through direct imaging have been in systems that had debris disks, and now we know the dust could be indicators of undiscovered worlds.”

Astronomers found the likelihood of finding long-period giant planets is nine times greater for stars with debris disks than stars without disks. Caltech graduate student Marta Bryan performed the statistical analysis that determined this result.

Researchers combined data from 130 single-star systems with debris disks detected by NASA’s Spitzer Space Telescope, and compared them with 277 stars that do not appear to host disks. The two star groups were between a few million and 1 billion years old. Of the 130 stars, 100 were previously scanned for exoplanets. As part of this study, researchers followed up on the other 30 using the W. M. Keck Observatory in Hawaii and the European Southern Observatory’s Very Large Telescope in Chile. They did not detect any new planets in those 30 systems, but the additional data helped characterize the abundance of planets in systems with disks.

The research does not directly resolve why the giant exoplanets would cause debris disks to form. Study authors suggest the massive gravity of giant planets causes small bodies called planetesimals to collide violently, rather than form proper planets, and remain in orbit as part of a disk.

“It’s possible we don’t find small planets in these systems because, early on, these massive bodies destroyed the building blocks of rocky planets, sending them smashing into each other at high speeds instead of gently combining,” said co-author Dimitri Mawet, a Caltech associate professor of astronomy and a JPL senior research scientist.

On the other hand, giant exoplanets are easier to detect than rocky planets, and it is possible that there are some in these systems that have not yet been found.

Our own solar system is home to gas giants responsible for making “debris belts” — the asteroid belt between Mars and Jupiter, shaped by Jupiter, and the Kuiper Belt, shaped by Neptune. Many of the systems Meshkat and Mawet studied also have two belts, but they are also much younger than ours — up to 1 billion years old, compared to our system’s present age of 4.5 billion years. The youth of these systems partly explains why they contain much more dust — resulting from the collisions of small bodies — than ours does.

One system discussed in the study is Beta Pictoris, which has been directly imaged from ground-based telescopes. This system has a debris disk, comets and one confirmed exoplanet. In fact, scientists predicted this planet’s existence well before it was confirmed, based on the presence and structure of the prominent disk.

In a different scenario, the presence of two dust belts in a single debris disk suggests there are likely more planets in the system whose gravity maintains these belts, as is the case in the HR8799 system of four giant planets. The gravitational forces of giant planets nudge passing comets inward toward the star, which could mimic the period of our solar system’s history about 4 billion years ago known as the Late Heavy Bombardment. Scientists think that during that period, the migration of Jupiter, Saturn, Uranus and Neptune deflected dust and small bodies into the Kuiper and asteroid belts we see today. When the Sun was young, there would have been a lot more dust in our solar system as well.

“By showing astronomers where future missions such as NASA’s James Webb Space Telescope have their best chance to find giant exoplanets, this research paves the way to future discoveries,” said Karl Stapelfeldt of JPL, chief scientist of NASA’s Exoplanet Exploration Program Office and study co-author.

The Moon Once Had An Atmosphere

A new study shows that an atmosphere was produced around the ancient Moon, 3 to 4 billion years ago, when intense volcanic eruptions spewed gases above the surface faster than they could escape to space. The study was published in Earth and Planetary Science Letters.

When one looks up at the Moon, dark surfaces of volcanic basalt can be easily seen to fill large impact basins. Those seas of basalt, known as maria, erupted while the interior of the Moon was still hot and generating magmatic plumes that sometimes breached the lunar surface and flowed for hundreds of kilometers. Analyses of Apollo samples indicate those magmas carried gas components, such as carbon monoxide, the ingredients for water, sulfur, and other volatile species.

In new work, Dr. Debra H. Needham, Research Scientist of NASA Marshall Space Flight Center, and Dr. David A. Kring, Senior Staff Scientist, at the Lunar and Planetary Institute, calculated the amounts of gases that rose from the erupting lavas as they flowed over the surface and showed that those gases accumulated around the Moon to form a transient atmosphere. The atmosphere was thickest during the peak in volcanic activity about 3.5 billion years ago and, when created, would have persisted for about 70 million years before being lost to space.

The two largest pulses of gases were produced when lava seas filled the Serenitatis and Imbrium basins about 3.8 and 3.5 billion years ago, respectively. The margins of those lava seas were explored by astronauts of the Apollo 15 and 17 missions, who collected samples that not only provided the ages of the eruptions, but also contained evidence of the gases produced from the erupting lunar lavas.

This new picture of the Moon has important implications for future exploration. The analysis of Needham and Kring quantifies a source of volatiles that may have been trapped from the atmosphere into cold, permanently shadowed regions near the lunar poles and, thus, may provide a source of ice suitable for a sustained lunar exploration program. Volatiles trapped in icy deposits could provide air and fuel for astronauts conducting lunar surface operations and, potentially, for missions beyond the Moon.

The new research was initiated from the LPI-Johnson Space Center’s Center for Lunar Science and Exploration, led by Kring and supported by NASA’s Solar System Exploration Research Virtual Institute. Needham is a former postdoctoral researcher at the LPI.

Volcano Erupts In Indonesia’s North Sumatra

JAKARTA: Mount Sinabung volcano in Karo district, Indonesia’s North Sumatra province erupted earlier Thursday, spewing a column of ash 2km into the sky, Xinhua news agency reported a disaster agency senior official as saying.

The eruption took place at 2.45am Jakarta time, followed by tremors with ash sliding 2km to the east and southeast, and 1.5km to the south of the crater, said spokesman for the national disaster management Sutopo Purwo Nugroho.

“But the eruption did not leave casualty and trigger fresh evacuation,” he told Xinhua in a text message.

On Wednesday, the volcano also erupted, spreading ash by up to 1.5km high, said Sutopo.

Mount Sinabung has been on top alert since July 2, 2015 with no-go zone of 7km in the south, southeast and east of the crater, according to him.

Mount Sinabung is one of Indonesia’s 129 active volcanoes.

UPDATE: Hurricane Ophelia Set To Tear Into UK This Weekend

The tail end of Hurricane Ophelia is set to barrel into the UK, lashing it with rain and winds of up to 70mph, forecasters have warned.

The tropical storm was upgraded to hurricane overnight and the remnants of it could reach the UK over the weekend or early next week.

Although Ophelia will not be strong enough to be categorised as a hurricane by the time it reaches Britain, the west of the country can expect gale-force winds.

Its arrival coincides with the 30th anniversary of the Great Storm of 1987, which hit southern England overnight on 15 October.

Forecaster Michael Fish famously told viewers not to worry about the storm, which killed 18 people and caused £1bn worth of damage.

Hurricane Ophelia is unlikely to cause as much damage as the Great Storm of 1987, which is often referred to as “Hurricane Fish”, but there is the possibility of disruptive weather.

Met Office forecaster Alex Burkhill said: “Ophelia became a hurricane overnight and the forecast track takes it eastwards towards Iberia for the weekend.

“After that, indications are that by that point it will then have weakened and be no longer a hurricane or tropical storm, it will be extratropical. But then it will continue its way towards the British Isles, probably reaching us very early next week.”

He added: “It’s definitely something that we are keeping an eye on, for the possibility of some disruptive weather early next week.”

Asteroid Tracking Network Observes Close Approach

On Oct. 12 EDT (Oct. 11 PDT), a small asteroid designated 2012 TC4 will safely pass by Earth at a distance of approximately 26,000 miles (42,000 kilometers). This is a little over one tenth the distance to the Moon and just above the orbital altitude of communications satellites. This encounter with TC4 is being used by asteroid trackers around the world to test their ability to operate as a coordinated international asteroid warning network.

2012 TC4 is estimated to be 50 to 100 feet (15 to 30 meters) in size. Orbit prediction experts say the asteroid poses no risk of impact with Earth. Nonetheless, its close approach to Earth is an opportunity to test the ability of a growing global observing network to communicate and coordinate its optical and radar observations in a real scenario.

This asteroid was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii in 2012. Pan-STARRS conducts a near-Earth object (NEO) survey funded by NASA’s NEO Observations Program, a key element of NASA’s Planetary Defense Coordination Office. However, 2012 TC4 traveled out of the range of asteroid-tracking telescopes shortly after it was discovered.

Based on the observations they were able to make in 2012, asteroid trackers predicted that it should come back into view in the fall of 2017. Observers with the European Space Agency and the European Southern Observatory were the first to recapture 2012 TC4, in late July 2017, using one of their large 8-meter aperture telescopes.Since then, observers around the world have been tracking the object as it approaches Earth and reporting their observations to the Minor Planet Center.

This “test” of what has become a global asteroid-impact early-warning system is a volunteer project, conceived and organized by NASA-funded asteroid observers and supported by the NASA Planetary Defense Coordination Office (PDCO).

As explained by Michael Kelley, program scientist and NASA PDCO lead for the TC4 observation campaign, “Asteroid trackers are using this flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid-impact threat.”

No asteroid currently known is predicted to impact Earth for the next 100 years.

Asteroid TC4’s closest approach to Earth will be over Antarctica at 1:42 AM EDT on Oct. 12 (10:42 p.m. PDT on Oct. 11). Tens of professionally run telescopes across the globe will be making ground-based observations in wavelengths from visible to near-infrared to radar. Amateur astronomers may contribute more observations, but the asteroid will be very difficult for backyard astronomers to see, as current estimates are that it will reach a visual magnitude of only about 17 at its brightest, and it will be moving very fast across the sky.

Many of the observers who are participating in this exercise are funded by NASA’s NEO Observations Program, but observers supported by other countries’ space agencies and space institutions around the world are now involved in the campaign.

Vishnu Reddy, an assistant professor at the University of Arizona’s Lunar and Planetary Laboratory in Tucson, is leading the 2012 TC4 campaign. Reddy is principal investigator for a NASA-funded near-Earth asteroid characterization project. “This campaign is a team effort that involves more than a dozen observatories, universities and labs around the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities,” he said. “This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications.”

In September, asteroid observers were able to conduct a “pre-test” of coordinated tracking of the close approach of a much larger asteroid known as 3122 Florence. Florence, one of the largest known NEOs, at 2.8 miles (4.5 kilometers) in size, passed by Earth on Sept. 1 at 18 times the distance to the Moon. Coordinated observations of this asteroid revealed, among other things, that Florence has two moons.

One Of Planet’s Largest Volcanic Eruptions

Washington State University researchers have determined that the Pacific Northwest was home to one of the Earth’s largest known volcanic eruptions, a millennia-long spewing of sulfuric gas that blocked out the sun and cooled the planet.

Only two other eruptions — the basalt floods of the Siberian Traps and the Deccan Traps — were larger, and they led to two of the Earth’s great extinctions.

“This would have been devastating regionally because of the acid-rain effect from the eruptions,” said John Wolff, a professor in the WSU School of the Environment. “It did have a global effect on temperatures, but not drastic enough to start killing things, or it did not kill enough of them to affect the fossil record.”

The research, which was funded by the National Science Foundation, appears in Geology, the top journal in the field. Starting 16.5 million years ago, they say, vents in southeast Washington and northeast Oregon put out a series of flows that reached nearly to Canada and all the way to the Pacific Ocean. The flows created the Wapshilla Ridge Member of the Grande Ronde Basalt, a kilometer-thick block familiar to travelers in the Columbia Gorge and most of Eastern Washington. The researchers say it is “the largest mapped flood basalt unit on Earth.”

The researchers estimate that, over tens of thousands of years, the floods put out between 242 and 305 billion tons of sulfur dioxide. That’s more than 4,000 times the output of the 1815 Mount Tambora eruption in present-day Indonesia. That eruption blanketed the Earth in an aerosol veil, creating the “Year Without A Summer” and food shortages across the northern hemisphere.

The volume of gas emitted from the Wapshilla Ridge lavas, said the researchers, “is equivalent to a Tambora eruption every day for 11 to 16 years.”

Most of the lava’s gases were released during the eruptions, but some of the gas remained trapped in crystals near the volcanic vents. Klarissa Davis, lead author of the paper, analyzed the gases as part of her doctoral studies. The other authors are Michael Rowe, now at the University of Auckland, and Owen Neill, now at the University of Michigan.

Wolff puts the eruption into one of three classes of cataclysms, the other two being a caldera eruption like the Yellowstone volcano and the impact of an asteroid. A similar eruption today “would devastate modern society globally,” said Wolff.

The eruption also provides an insight into the workings of climate change. It took place in what is known as the Miocene Climactic Optimum, or MCO, when some 50 million years of cooling was interrupted by 5 to 6 degrees Fahrenheit of warming. But at its peak, the MCO had a brief cooling period that coincides with the Wapshilla eruption and its profusion of sulfur dioxide.

Sulfur dioxide is now bandied about as a possible tool for engineering a break in the Earth’s current warming trend, though Wolff is not particularly keen on the idea.

“I personally think that it’s probably a dangerous thing to do without understanding all of the possible consequences,” he said. “But maybe we’re getting an idea of some possible consequences here.”