Month: May 2018

Recent Work Challenges View Of Early Mars, Picturing A Warm Desert With Occasional Rain

The climate of early Mars is a subject of debate. While it has been thought that Mars had a warm and wet climate, like Earth, other researchers suggested early Mars might have been largely glaciated. A recent study by Ramses Ramirez from the Earth-Life Science Institute (Tokyo Institute of Technology, Japan) and Robert Craddock from the National Air and Space Museum’s Center for Earth and Planetary Studies (Smithsonian Institution, USA) suggests that the early Martian surface may not have been dominated by ice, but instead it may have been modestly warm and prone to rain, with only small patches of ice.

While there is little debate about whether water previously existed on Mars, the debate regarding what the climate of Mars was like around 4 billion years ago has persisted for decades. Mars has a surprisingly diverse landscape, made up of valley networks, lake basins and possible ocean shorelines. These ancient fluvial features all provide clues that early Mars may have had a warm and wet climate, similar to Earth’s.

However, this idea has challenges. First, the amount of solar energy entering the atmosphere at the time was considered to be too low to support a warm and wet climate. Secondly, recent climate studies have argued that Mars’ ancient fluvial features can be accounted for with an icy climate, where widespread surfaces of ice promoted cooling by reflecting solar radiation. Occasional warming events would have triggered large amounts of ice-melt, and fluvial activity as a result. However, Ramses Ramirez (Earth-Life Science Institute, Japan) and Robert Craddock (Smithsonian Institution, USA) suggest that early Mars was probably warm and wet, and not so icy, after a careful geological and climatological analysis revealed little evidence of widespread glaciation.

Recently, the authors’ study, published in Nature Geoscience, argues that volcanic activity on a relatively unglaciated planet could explain Mars’ fluvial features. Volcanic eruptions releasing CO2, H2, and CH4 may have contributed to the greenhouse effect, which in turn may have promoted warming, precipitation (including rain), and the flow of water that carved out the valleys and fluvial features. However, this climate would not have been as warm and wet as Earth’s, with precipitation rates of around 10 centimeters per year (or less), similar to Earth’s semi-arid regions. This drier climate suggests that small amounts of ice deposits could have also existed, though these would have been thin, and liable to melt, contributing to the fluvial system.

In the future, the authors will be using more complex models in their analysis to investigate their warm, semi-arid climate hypothesis further. They will also be aiming to find out what the climate was like before these fluvial features formed on Mars. This will involve investigating the earliest history of Mars, which is a mysterious subject since little is currently known about it.

Taming The Multiverse: Stephen Hawking’s Final Theory About The Big Bang

Professor Stephen Hawking’s final theory on the origin of the universe, which he worked on in collaboration with Professor Thomas Hertog from KU Leuven, has been published today in the Journal of High Energy Physics.

The theory, which was submitted for publication before Hawking’s death earlier this year, is based on string theory and predicts the universe is finite and far simpler than many current theories about the big bang say.

Professor Hertog, whose work has been supported by the European Research Council, first announced the new theory at a conference at the University of Cambridge in July of last year, organised on the occasion of Professor Hawking’s 75th birthday.

Modern theories of the big bang predict that our local universe came into existence with a brief burst of inflation — in other words, a tiny fraction of a second after the big bang itself, the universe expanded at an exponential rate. It is widely believed, however, that once inflation starts, there are regions where it never stops. It is thought that quantum effects can keep inflation going forever in some regions of the universe so that globally, inflation is eternal. The observable part of our universe would then be just a hospitable pocket universe, a region in which inflation has ended and stars and galaxies formed.

“The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean,” said Hawking in an interview last autumn. “The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse. But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite the theory can’t be tested. ”

In their new paper, Hawking and Hertog say this account of eternal inflation as a theory of the big bang is wrong. “The problem with the usual account of eternal inflation is that it assumes an existing background universe that evolves according to Einstein’s theory of general relativity and treats the quantum effects as small fluctuations around this,” said Hertog. “However, the dynamics of eternal inflation wipes out the separation between classical and quantum physics. As a consequence, Einstein’s theory breaks down in eternal inflation.”

“We predict that our universe, on the largest scales, is reasonably smooth and globally finite. So it is not a fractal structure,” said Hawking.

The theory of eternal inflation that Hawking and Hertog put forward is based on string theory: a branch of theoretical physics that attempts to reconcile gravity and general relativity with quantum physics, in part by describing the fundamental constituents of the universe as tiny vibrating strings. Their approach uses the string theory concept of holography, which postulates that the universe is a large and complex hologram: physical reality in certain 3D spaces can be mathematically reduced to 2D projections on a surface.

Hawking and Hertog developed a variation of this concept of holography to project out the time dimension in eternal inflation. This enabled them to describe eternal inflation without having to rely on Einstein’ theory. In the new theory, eternal inflation is reduced to a timeless state defined on a spatial surface at the beginning of time.

“When we trace the evolution of our universe backwards in time, at some point we arrive at the threshold of eternal inflation, where our familiar notion of time ceases to have any meaning,” said Hertog.

Hawking’s earlier ‘no boundary theory’ predicted that if you go back in time to the beginning of the universe, the universe shrinks and closes off like a sphere, but this new theory represents a step away from the earlier work. “Now we’re saying that there is a boundary in our past,” said Hertog.

Hertog and Hawking used their new theory to derive more reliable predictions about the global structure of the universe. They predicted the universe that emerges from eternal inflation on the past boundary is finite and far simpler than the infinite fractal structure predicted by the old theory of eternal inflation.

Their results, if confirmed by further work, would have far-reaching implications for the multiverse paradigm. “We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes,” said Hawking.

This makes the theory more predictive and testable.

Hertog now plans to study the implications of the new theory on smaller scales that are within reach of our space telescopes. He believes that primordial gravitational waves — ripples in spacetime — generated at the exit from eternal inflation constitute the most promising “smoking gun” to test the model. The expansion of our universe since the beginning means such gravitational waves would have very long wavelengths, outside the range of the current LIGO detectors. But they might be heard by the planned European space-based gravitational wave observatory, LISA, or seen in future experiments measuring the cosmic microwave background.

NASA Will Solve a Massive Physics Mystery This Summer

It takes 512 years for a high-energy photon to travel from the nearest neutron star to Earth. Just a few of them make the trip. But they carry the information necessary to solve one of the toughest questions in astrophysics.

The photons shoot into space in an energetic rush. Hot beams of X-ray energy burst from the surface of the tiny, ultradense, spinning remnant of a supernova. The beams disperse over long centuries in transit. But every once in a while, a single dot of X-ray light that’s traveled 156 parsecs (512 light-years) across space — 32 million times the distance between Earth and the sun — expends itself against the International Space Station’s (ISS) X-ray telescope, nicknamed NICER. Then, down on Earth, a text file enters a new point of data: the photon’s energy and its arrival time, measured with microsecond accuracy.

That data point, along with countless others like it collected over the course of months, will answer a basic question as soon as summer 2018: Just how wide is J0437-4715, Earth’s nearest neutron-star neighbor?

If researchers can figure out the width of a neutron star, physicist Sharon Morsink told a crowd of scientists at the American Physical Society’s (APS) April 2018 meeting, that information could point the way toward solving one of the great mysteries of particle physics: How does matter behave when pushed to its wildest extremes? [10 Futuristic Technologies ‘Star Trek’ Fans Would Love]

On Earth, given humanity’s existing technology, there are some hard limits on how dense matter can get, even in extreme laboratories, and even harder limits on how long the densest matter scientists make can survive. That’s meant that physicists haven’t been able to figure out how particles behave at extreme densities. There just aren’t many good experiments available.

“There’s a number of different methodologies that people come up with to try to say how super-dense matter should behave, but they don’t all agree,” Morsink, a physicist at the University of Alberta and a member of a NASA working group focused on the width of neutron stars, told Live Science. “And the way that they don’t all agree can actually be tested because each one of them makes a prediction for how large a neutron star can be.”

In other words, the solution to the mystery of ultradense matter is locked away inside some of the universe’s densest objects — neutron stars. And scientists can crack that mystery as soon as they measure precisely just how wide (and, therefore, dense) neutron stars really are.

“Neutron stars are the most outrageous objects that most people have never heard of,” NASA scientist Zaven Arzoumanian told physicists at the meeting in Columbus, Ohio.

Arzoumanian is one of the heads of NASA’s Neutron Star Interior Composition Explorer (NICER) project, which forms the technical basis for Morsink’s work. NICER is a large, swiveling telescope mounted on the ISS; it monitors and precisely times the X-rays that arrive in the area of low Earth orbit from deep space.

A neutron star is the core left behind after a massive supernova explosion, but it’s believed to be not much wider than a midsize city. Neutron stars can spin at high fractions of the speed of light, firing flickering beams of X-ray energy into space with more precise timing than the ticking of atomic clocks.

And most importantly for Morsink and her colleagues’ purposes, neutron stars are the densest known objects in the universe that haven’t collapsed into black holes — but unlike with black holes, it’s possible for scientists to figure out what goes on inside them. Astronomers just need to know precisely how wide neutron stars really are, and NICER is the instrument that should finally answer that question.

Scientists don’t know exactly how matter behaves in the extreme core of a neutron star, but they understand enough to know that it’s very weird.

Daniel Watts, a particle physicist at the University of Edinburgh, told a separate audience at the APS conference that the interior of a neutron star is essentially a great big question mark.

Scientists have some excellent measurements of the masses of neutrons stars. The mass of J0437-4715, for example, is about 1.44 times that of the sun, despite being more or less the size of Lower Manhattan. That means, Morsink said, that J0437-4715 is far denser than the nucleus of an atom — by far the densest object that scientists encounter on Earth, where the vast majority of an atom’s matter gathers in just a tiny speck in its center.

At that level of density, Watts explained, it’s not at all clear how matter behaves. Quarks, the tiny particles that make up neutrons and protons, which make up atoms, can’t exist freely on their own. But when matter reaches extreme densities, quarks could keep binding into particles similar to those on Earth, or form larger, more complex particles, or perhaps mush together entirely into a more generalized particle soup. [7 Strange Facts About Quarks]

What scientists do know, Watts told Live Science, is that the details of how matter behaves at extreme densities will determine just how wide neutron stars actually get. So if scientists can come up with precise measurements of neutron stars, they can narrow down the range of possibilities for how matter behaves under those extreme conditions.

And answering that question, Watts said, could unlock answers to all sorts of particle-physics mysteries that have nothing to do with neutron stars. For example, he said, it could help answer just how individual neutrons arrange themselves in the nuclei of very heavy atoms.

Most neutron stars, Morsink said, are believed to be between about 12 and 16 miles (20 and 28 kilometers) wide, though they might be as narrow as 10 miles (16 km). That’s a very narrow range in astronomy terms but not quite precise enough to answer the kinds of questions Morsink and her colleagues are interested in.

To press toward even more precise answers, Morsink and her colleagues study X-rays coming from rapidly spinning “hotspots” on neutron stars.

Though neutron stars are incredibly compact spheres, their magnetic fields cause the energy coming off of their surfaces to be fairly uneven. Bright patches form and mushroom on their surfaces, whipping around in circles as the stars turn many times a second.

That’s where NICER comes in. NICER is a large, swiveling telescope mounted on the ISS that can time the light coming from those patches with incredible regularity.

That allows Morsink and her colleagues to study two things, both of which can help them figure out a neutron star’s radius:

1. The speed of rotation: When the neutron star spins, Morsink said, the bright spot on its surface winks toward and away from Earth almost like the beam from a lighthouse turning circles. Morsink and her colleagues can carefully study NICER data to determine both exactly how many times the star is winking each moment and exactly how fast the bright spot is moving through space. And the speed of the bright spot’s motion is a function of the star’s rate of rotation and its radius. If researchers can figure out the rotation and speed, the radius is relatively easy to determine.

2. Light bending: Neutron stars are so dense that NICER can detect photons from the star’s bright spot that fired into space while the spot was pointed away from Earth. A neutron star’s gravity well can bend light so sharply that its photons turn toward and smack into NICER’s sensor. The rate of light curvature is also a function of the star’s radius and its mass. So, by carefully studying how much a star with a known mass curves light, Morsink and her colleagues can figure out the star’s radius.

And the researchers are close to announcing their results, Morsink said. (Several physicists at her APS talk expressed some light disappointment that she hadn’t announced a specific number, and excitement that it was coming.)

Morsink told Live Science that she wasn’t trying to tease the upcoming announcement. NICER just hasn’t collected enough photons yet for the team to offer up a good answer.

“It’s like taking a cake out of the oven too early: You just end up with a mess,” she said.

But the photons are arriving, one by one, during NICER’s months of periodic study. And an answer is getting close. Right now, the team is looking at data from J0437-4715 and Earth’s next-nearest neutron star, which is about twice as far away.

Morsink said she isn’t sure which neutron star’s radius she and her colleagues will publish first, but she added that both announcements will be coming within months.

“The aim is for this to happen later on this summer, where ‘summer’ is being used in a fairly broad sense,” she said. “But I would say that by September, we ought to have something.”

Activity on Hawaii Volcano Could Indicate New Eruption

A series of earthquakes and the collapse of the crater floor at the Puu Oo vent on Hawaii’s Kilauea Volcano could trigger a new eruption of lava, officials said Tuesday.

Scientists from the U.S. Geological Survey’s Hawaiian Volcano Observatory said that seismic activity over the past 24 hours could lead to a new breakout on the east side of the Big Island volcano.

USGS geologist Janet Babb said similar activity has been recorded prior to previous eruptions in the area. In mid-April the observatory issued a volcano activity alert when scientists noticed the Puu Oo vent was inflating and becoming pressurized.

“We knew that change was afoot and we’ve seen this in the past, and so we have been kind of waiting and watching for whatever change that was going to happen to happen,” Babb said. “It happened yesterday afternoon.”

When the earthquakes and collapse occurred and the pressure within the Puu Oo vent was released, an “intrusion” of lava was sent into a new area of the volcano and spread throughout the night.

“Magma has now migrated into a lower part of the East Rift Zone,” Babb said. “The concern is that the intrusion migrated about 10 miles down rift into the area where Highway 130 is.”

There are homes in that area of the Big Island and Highway 130 leads to a popular access point where people can hike or bike into the lava viewing area.

The Hawaii County Civil Defense Agency sent out an alert Tuesday morning warning residents in the area to monitor the situation and be prepared for the possibility of a new lava flow.

Spokeswoman Kanani Aton said that the agency is “planning ahead for a worst-case scenario” by reviewing emergency plans and monitoring the activity in conjunction with USGS officials.

All public access from the island’s Puna District near Kalapana has been shut down and visitors have been warned to stay away in case of an eruption. Private excursions including boat and hiking tours have also been suspended.

“It’s been closed due to the possibility of an eruption and security has been posted to ensure that no unauthorized persons enter,” Aton said, adding that anywhere from 500 to 2,000 people visit the site each day. “It is important to note that although there is increased seismic activity in the area, the magnitude is not large enough to cause concern for tsunami.”

Babb says the activity has slowed significantly since a spike on Monday afternoon and overnight, but the threat level has not changed. Scientists don’t know if decreased seismic activity is an indication that the event is over or if it’s just stalled and could pick back up.

“That’s the unknown at this point. Therefore we are still watching, we are watching very closely,” Babb said.

Geologists flew over the area and observed a layer of red ash covering the ground near the Puu Oo vent. The ash was spread throughout the area when the crater floor collapsed.

“The good news is that as they flew down the East Rift Zone they didn’t see any ground cracks or steaming that would suggest that the magma was coming near the surface,” Babb said.

Most of Kilauea’s activity has been nonexplosive, but a 1924 eruption spewed ash and 10-ton rocks into the sky, leaving one man dead.

Puu Oo’s 1983 eruption resulted in lava fountains soaring over 1,500 feet high. In the decades since, the lava flow has buried dozens of square miles (kilometers) of land and destroyed many homes.

In 2008, after a series of small earthquakes rattled the island, Kilauea’s summit crater opened and gushed lava and rock over 75 acres of the mountain, damaging a nearby visitor overlook.