New Results Indicate Interstellar Nomad `Oumuamua Is A Comet

`Oumuamua — the first interstellar object discovered within our Solar System — has been the subject of intense scrutiny since its discovery in October 2017. Now, by combining data from the ESO’s Very Large Telescope and other observatories, an international team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumuamua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial mechanics.

The team, led by Marco Micheli (European Space Agency) explored several scenarios to explain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely explanation is that `Oumuamua is venting material from its surface due to solar heating — a behaviour known as outgassing. The thrust from this ejected material is thought to provide the small but steady push that is sending `Oumuamua hurtling out of the Solar System faster than expected — as of 1 June 2018 it is traveling at roughly 114,000 kilometres per hour.

Such outgassing is a behaviour typical for comets and contradicts the previous classification of `Oumuamua as an interstellar asteroid. “We think this is a tiny, weird comet,” commented Marco Micheli. “We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets.”

Usually, when comets are warmed by the Sun they eject dust and gas, which form a cloud of material — called a coma (cometary) — around them, as well as the characteristic tail . However, the research team could not detect any visual evidence of outgassing.

“We did not see any dust, coma, or tail, which is unusual,” explained co-author Karen Meech of the University of Hawaii, USA. Meech led the discovery team’s characterisation of `Oumuamua in 2017. “We think that ‘Oumuamua may vent unusually large, coarse dust grains.”

The team speculated that perhaps the small dust grains adorning the surface of most comets eroded during `Oumuamua’s journey through interstellar space, with only larger dust grains remaining. Though a cloud of these larger particles would not be bright enough to be detected, it would explain the unexpected change to ‘Oumuamua’s speed.

Not only is `Oumuamua’s hypothesised outgassing an unsolved mystery, but also its interstellar origin. The team originally performed the new observations on `Oumuamua to exactly determine its path which would have probably allowed it to trace the object back to its parent star system. The new results means it will be more challenging to obtain this information.

“The true nature of this enigmatic interstellar nomad may remain a mystery,” concluded team member Olivier Hainaut, an astronomer at ESO. “`Oumuamua’s recently-detected gain in speed makes it more difficult to be able to trace the path it took from its extrasolar home star.”

Study Yields A New Scale Of Earthquake Understanding

CHAMPAIGN, Ill. — Nanoscale knowledge of the relationships between water, friction and mineral chemistry could lead to a better understanding of earthquake dynamics, researchers said in a new study. Engineers at the University of Illinois at Urbana-Champaign used microscopic friction measurements to confirm that, under the right conditions, some rocks can dissolve and may cause faults to slip.

The study, published in the journal Nature Communications, closely examines how water and calcite – a mineral that is very common in the Earth’s crust – interact at various pressures and groundwater compositions to influence frictional forces along faults.

“Water is everywhere in these systems,” said Rosa Espinosa-Marzal, a civil and environmental engineering professor and co-author of the study. “There is water on the surface of minerals and in the pore spaces between mineral grains in rocks. This is especially true with calcite-containing rocks because of water’s affinity to the mineral.”

According to the researchers, other studies have correlated the presence of water with fault movement and earthquakes, but the exact mechanism remained elusive. This observation is particularly prevalent in areas where fracking operations are taking place – a process that involves a lot of water.

The study focuses on calcite-rich rocks in the presence of brine – naturally occurring salty groundwater – along fault surfaces. The rock surfaces that slide past each other along faults are not smooth. The researchers zoomed in on the naturally occurring tiny imperfections or unevenness on rocks’ surfaces, called asperities, at which friction and wear originate when the two surfaces slide past each other.

“The chemical and physical properties of faulted rocks and mechanical conditions in these systems are variable and complex, making it difficult to take every detail into account when trying to answer these types of questions,” Espinosa-Marzal said. “So, to help understand water’s role in fault dynamics, we looked at a scaled-down, simplified model by examining single asperities on individual calcite crystals.”

For the experiments, the team submerged calcite crystals in brine solutions at various concentrations and subjected them to different pressures to simulate a natural fault setting. Once the crystals were in equilibrium with the solution, they used an atomic force microscope to drag a tiny arm with a silicon tip – to simulate the asperity – across the crystal to measure changes in friction.

In most of the experiments, the researchers first found what they expected: As the pressure applied on the crystals increased, it became more difficult to drag the tip across the crystal’s surface. However, when they increased pressure to a certain point and the tip was moved slowly enough, the tip began to slide more easily across the crystal.

“This tells us that something has happened to this tiny asperity under higher pressures that caused a decrease in friction,” said graduate student and co-author Yijue Diao. “The atomic force microscope also allows us to image the crystal surface, and we can see that the groove increased in size, confirming that calcite had dissolved under pressure. The dissolved mineral and water acted as a good lubricant, thereby causing the observed weakening of the single-asperity contact.”

“This shows that studies such as these warrant serious consideration in future work,” Espinosa-Marzal said. The researchers acknowledge that there are still many questions to address related to this research. However, their work demonstrates that certain brine-calcite interactions, under applied stress, induce dissolution and decrease the frictional strength at the single-asperity scale.

“Our research also suggests that it might be possible to mitigate earthquake risk by purposely changing brine compositions in areas that contain calcite-rich rocks. This consideration could be beneficial in areas where fracking is taking place, but this concept requires much more careful investigation,” Espinosa-Marzal said.

“As a young scientist who works at the nanoscale, I never thought that earthquake dynamics would be the type of thing I would be researching,” Diao said. “However, we have learned so much about things at the macroscale that nanoscale studies like ours can reveal new critical insights into many large-scale natural phenomena.”

Tornado Injures 8 In Kansas Town, Part Of Towering, ‘Jaw-Dropping’ Complex Of Storms

A tornado ripped through the town of Eureka, Kan., on Tuesday, injuring eight people. Gov. Jeff Colyer declared a state of emergency for the area because of widespread damage.

The tornado was part of a violent yet visually stunning complex of storms that left storm chasers in awe.

Eureka, home to about 2,450 residents, is located about 60 miles east of Wichita in Greenwood County. The town reportedly took a “direct hit” from the tornado and the Red Cross opened a shelter for storm victims. reported the storm knocked out power to at least 1,300 customers and left behind extensive tree damage.

The National Weather Service forecast office in Wichita said it is sending a team to assess the tornado damage and will classify the storm on the 0 to 5 Enhanced Fujita rating scale.

The complex of storms that spawned the Eureka twister tore through central and eastern Kansas on Tuesday, resulting in numerous instances of damaging winds and large hail, up to the size of eggs.

Storm satellite imagery showed the thunderstorm complex shooting up tens of thousands of feet into the atmosphere.

Photographers and storm chasers caught images of towering rotating thunderstorms that resembled spaceships. “Some of the most stunning storm structure I’ve seen,” tweeted Travis Heying, a photojournalist for the Wichita Eagle. Stephen Jones, a storm chaser, called the sky scenery “jaw-dropping.”

In the storm’s wake, dramatic mammatus clouds covered the sky, illuminated by the sun dropping beneath the horizon. “Many, many people are saying they have never seen ‘clouds like that,’” said Mike Smith, a retired meteorologist in Wichita. Smith shared the photo below.

‘Ring Around Bathtub’ At Giant Volcano Field Shows Movement Of Subterranean Magma

The Laguna del Maule volcanic complex in Chile is a large, complicated and explosive landscape that, oddly, lacks the classic cone seen on many volcanoes, including Fuego, the Guatemalan volcano that killed hundreds in a June 3 eruption.

It’s a major task to understand a mountaintop region that has erupted 50 times over the past 20,000 years. But the starting point for grasping the big picture of a study published today (June 27) in Science Advances is pretty simple: It’s the ring that standing water leaves on a bathtub.

Like the shore of an ancient lake, a bathtub ring must be horizontal when it forms. But, as University of Wisconsin-Madison professor of geoscience Brad Singer noticed years ago, the ancient, elevated shoreline at Maule now slopes from a low spot in the north to a high spot in the south.

The Maule volcanoes, located in a region that has seen enormous eruptions during the last million years, are restless. Since 2007, satellite instruments have measured an average uplift of 8 inches per year—far and away the fastest and longest measured rise of a restless volcano in the world, and an unmistakable sign that molten rock under the area is rising.

Singer, a volcanologist and specialist in dating rocks, currently directs a five-year National Science Foundation project to explore Maule with a wide variety of geologic techniques. Understanding why that rise is taking place, and what it portends, are two central goals of the project, which brought dozens of scientists and students to the site.

Generally, volcanology is a rearview-mirror exercise. Months, years, or even 50 million years after the lava cools and the ash settles, scientists examine the chemistry, shape, and distribution of rocks in a forensic effort to understand a volcanic site. At Laguna del Maule, among the most active volcanic regions in the world, Singer is trying to document conditions and processes before the next eruption.

Chile has more than 80 volcanoes. Maule, along with many others, erupts rhyolite, a particularly explosive kind of molten rock. Rhyolite contains a high level of water and carbon dioxide, which both flash to gas as pressure drops when the magma approaches earth’s surface.

Knowing the rate and variations of magma rising into a reservoir beneath a volcano is critical to questions about future eruptions, but measurements of rock properties up to a dozen miles underground must, by definition, be indirect.

The goal, Singer says, “Is to build a mental picture, a model, for the mechanisms that operate before a large, or ‘super’ eruption.”

The study in Science Advances used the ancient shoreline for baseline information about the area’s landscape 10,000 years ago. That was when a rhyolite lava flow that “plugged” the lake’s outlet collapsed, dropping the water level by about 200 meters down to its present level.

The relic shoreline was at least 60 kilometers long, although much of it has since been covered by lava flows. During four field trips, Singer and colleagues used precise GPS instruments to get altitude measurements at 64 points along the shoreline.

The highest point, they found, was 62 meters above the lowest point, allowing the researchers to calculate an average rise of 6 millimeters per year. But if the current rapid uplift following a period of stability is typical, the total uplift likely occurred in as many as 16 rapid pulses, averaging 50 years each, during the past 10,000 or so years.

The baseline information on uplift was then combined with data on earth shaking, gravity and electrical conductivity, and analyses of minerals at the surface—the relics of past eruptions—to paint a better picture of the geologic situation.

Hélène Le Mével, a UW-Madison geoscience Ph.D. and paper co-author, used the warping of the shoreline to estimate the shape, size and depth of the magma body that grew beneath the southern end of the lake. The body is 7 kilometers deep and has a shape something like an egg.

Since the natural lava dam burst and the lake level fell, the researchers calculated that 13 cubic kilometers of magma rose into this reservoir to create the magma body that raised the overlying volcanic region.

In the same period, another nine cubic kilometers of magma has erupted.

A clarified view of the pace and details of the uplift helped Singer’s team address two pressing issues in volcanology:

What role do fluids play in causing uplift at the biggest, most dangerous volcanoes? Volcanic uplift can be caused by rising magma, or by pressurized liquid or gas. If the researchers are correct that periods of uplift alternated with periods of stability over 9,400 years, then the magma must have been cooling into solid rock. Otherwise, each eruption would have allowed fluid and gas to escape, causing deflation.

What determines whether the magma reservoir erupts or freezes into a giant, homogenous rock body like Half Dome (called a pluton)? Can both phenomena occur in the same pool of magma at the essentially the same time? “Here, we have evidence that the same magma reservoir can sustain both processes,” says Singer. “The magma reservoir is slowly growing for thousands of years, at a shallow depth, and some of it is freezing, but during the same period, it’s also erupting.”

As for Maule itself, the rate of rise seems to be slowing after 11 race-car years. That likely reduces the probability of an eruption in the near term, which is good news to Chileans, and to Argentines, who live downwind from this border-straddling complex. Maule’s alert status is currently low on the list of more than 40 hazardous volcanoes that Chile’s Southern Andes Volcano Observatory monitors.

But that’s not the end of the story, says Singer. Even if the magma intrusions at Maule slowly grind to a halt, other factors could trigger an eruption.

Chile, part of the Ring of Fire, was site of two of the four most intense earthquakes in the past century. Moreover, even as uplift declines, an earthquake along a small local fault could promote enough movement of magma to trigger another eruption at Maule, Singer says.

Galapagos’ Sierra Negra Volcano Eruption Triggers Evacuation

The Sierra Negra volcano on the Galapagos island of Isabela is spewing fountains of lava and plumes of ash.

Fifty people have been evacuated from the surrounding area and tourists have been barred from visiting it.

The eruption started after two strong earthquakes opened up fissures in the 1,124m-high (3688ft) volcano.

It comes 11 days after the Cumbre volcano, the most active on the Galapagos, erupted on the uninhabited island of Fernandina.

The Sierra Negra volcano is located on the south-eastern tip of Isabela, the largest of the 18 main islands which make up the Galapagos Archipelago.

The Galapagos which are located about 1,000km (621 miles) off the coast of Ecuador are one of the most volcanically active regions in the world.

Sierra Negra last erupted in 2005. Night-time photos showed lava flowing down to the sea.

Thousands of tourists visit the Galapagos Islands every year, drawn by its unique biodiversity and its pristine environment.

The variety of wildlife on the island famously inspired Charles Darwin to conceive the theory of evolution.

Hawaii Volcano: Growing Crater Knocks Out GPS Station, May Devour Museum At Summit

The summit crater of Hawaii’s Kilauea Volcano has grown dramatically large since the latest eruption began in May, so large that it may be threatening a museum at Hawaii Volcanoes National Park.

The U.S. Geological Survey said in a Twitter post on Monday that a GPS station location in the Halemaumau Crater was knocked out of service after subsiding 310 feet as the subsidence continues to grow.

Since the eruption started on May 3, sending magma spewing out along fissures in the eastern Puna region of the island, the volcano’s crater has been subsiding. That has caused near-daily earthquakes, rock falls and subsequent explosions at the summit.

“The current slumping and rocksliding is a response to magma draining from the former summit lava lake. However, we don’t know if or when the lake might reappear,” the agency said on Twitter.

The USGS said over the weekend that over 350 earthquakes greater than magnitude 2.5 were reported in a 24-hour peroid at the summit.

On Sunday, the USGS conducted a drone flight over the crater area, showing the dramatic changes as the lava has drained out. According to USGS, the deepest part of Halemaumau is now over 1,300 feet below the caldera floor.

A Galactic Test To Clarify The Existence Of Dark Matter

Researchers at the University of Bonn and the University of California at Irvine used sophisticated computer simulations to devise a test that could answer a burning question in astrophysics: does dark matter actually exist? Or does Newton’s gravitational law need to be modified? The new study, now published in the Physical Review Letters, shows that the answer is hidden in the motion of the stars within small satellite galaxies swirling around the Milky Way.

Using one of the fastest supercomputers in the world, the scientists have simulated the matter distribution of the so-called satellite “dwarf” galaxies. These are small galaxies that orbit larger galaxies like the Milky Way or Andromeda.

The researchers focused on a relationship called radial acceleration relation (RAR). In disk galaxies, stars move in circular orbits around the galactic center. The acceleration that forces them to change direction is caused by the attraction of matter in the galaxy. The RAR describes the relationship between this acceleration and the one caused by the visible matter only. It provides an insight into the structure of galaxies and their matter distribution.

“We have now simulated, for the first time, the RAR of dwarf galaxies on the assumption that dark matter exists,” explains Prof. Dr. Cristiano Porciani of the Argelander Institute for Astronomy at the University of Bonn. “It turned out that they behave as scaled-down versions of larger galaxies.” But what if there is no dark matter and instead gravity works differently than Newton thought? “In this case, the RAR of dwarf galaxies depends strongly on the distance to their parent galaxy, while this does not happen if dark matter exists,” explains researcher Emilio Romano-Díaz.

This difference makes the satellites a powerful probe for testing whether dark matter really exists. The Gaia spacecraft, which was launched by the European Space Agency (ESA) in 2013, could provide an answer. It was designed to study the stars in the Milky Way and its satellite galaxies in unprecedented detail and has collected a large amount of data.

However, it will probably take years to analyze the data. “Individual measurements are not enough to test the small differences we have found in our simulations,” explains doctoral student Enrico Garaldi. “But repeatedly examining the same stars improves the measurements every time. Sooner or later, it should be possible to determine whether the dwarf galaxies behave as in a universe with dark matter—or not.”

The cement that holds galaxies together

This question is one of the most pressing issues in cosmology today. The existence of dark matter was suggested more than 80 years ago by the Swiss astronomer Fritz Zwicky. He realized that galaxies move so fast within galaxy clusters that they should actually drift apart. He therefore postulated the presence of invisible matter which, due to its mass, exerts sufficient gravity to keep galaxies on their observed orbits. In the 1970s, his U.S. colleague Vera Rubin discovered a similar phenomenon in spiral galaxies like the Milky Way—they rotate so quickly that the centrifugal force should tear them apart if only visible matter was present.

Today, most physicists are convinced that dark matter makes up about 80 percent of the mass in the universe. Since it does not interact with light, it is invisible to telescopes. Yet, assuming its existence provides an excellent fit to a number of other observations—such as the distribution of background radiation, the afterglow of the Big Bang. Dark matter also provides a good explanation for the arrangement and formation rate of galaxies in the universe. However, despite numerous experimental efforts, there is no direct proof that dark matter exists. This led astronomers to the hypothesis that the gravitational force itself might behave differently than previously thought. According to the theory called modified Newtonian dynamics (MOND), the attraction between two masses obeys Newton’s laws only up to a certain point. At very small accelerations, such as those prevailing in galaxies, gravity becomes considerably stronger. Therefore, galaxies do not tear apart due to their rotational speed and the MOND theory can dispense with dark matter.

The new study opens up the possibility for astronomers to test these two hypotheses in an unprecedented regime.