Giant planets could reach 'maturity' much earlier than previously thought, study reveals

An international team of scientists, in which researchers from the Instituto de Astrofísica de Canarias (IAC) participate together with other institutions from Spain, Italy, Germany, Belgium, UK, and Mexico, has been able to measure the masses of the giant planets of the V1298 Tau system, just 20 million year old. Masses for such young giant planets had not been obtained previously, and this is the first evidence that these objects have already reached their final size at very early stages of their evolution. For this study they have used radial velocity measurements from the HARPS-N spectrographs, at the Roque de los Muchachos Observatory (ORM), and CARMENES, at the Calar Alto Observatory. The results are published today in the journal Nature Astronomy.

The study, led by the IAC researcher Alejandro Suárez Mascareño, reports the measurement of the masses of two giant planets that orbit the young solar-type star V1298 Tau. They were discovered in 2019 by a team lead by Trevor David (JPL) using data from NASA's Kepler space telescope, which allowed the measurement of their sizes, slightly smaller than Jupiter, and of their orbital periods, 24 and 40 days for V1298 Tau b and e, respectively.

"The characterization of very young planets is extraordinarily difficult," says Alejandro Suárez Mascareño, first author of the publication. The parent stars have very high levels of activity and until very recently it was unthinkable to even try ." And he adds: "Only thanks to the combination of detections made with space telescopes, combined with intense radial velocity campaigns from Earth-based observatories and the use of the most advanced analysis techniques, it was possible to begin to see what is happening in such early stages of the evolution of planetary systems ." In fact, for the new measurements of the planetary masses, it was necessary to separate the signals generated by these planets from the signal generated by the star's activity, almost ten times larger.

The study shows that the masses and radii of the planets V1298 Tau b and c are surprisingly similar to those of the giant planets of the Solar System or in other old extra-solar systems. These measurements, which are the first to be obtained of such young giant planets, allow us to test current ideas about the formation of planetary systems. "For many years, theoretical models have indicated that giant planets begin their evolution as bodies with a larger size, and later they contract over hundreds millions or even billions of years '', explains Víctor J. Sánchez Béjar, researcher at the IAC and co-author of the work. "We now know that they can actually reach a size similar to that of the planets in the Solar System in a very short time," he notes.

The study of young systems gives researchers clues about what happened during the infancy of our solar system. "We still do not know if V1298 Tau is a normal case and its evolution is similar to that of most planets or if we are facing an exceptional case; if this were the normal scenario, it would mean that the evolution of planets like Jupiter and Saturn could have been very different from what we think ," comments Nicolas Lodieu, a researcher at the IAC and also a co-author of the work. The results of this work thus help to build a more solid idea of the early evolution of planetary systems like ours.

To achieve the measurement of these masses, the study has required a significant observational effort and the collaboration of multiple observatories and institutions from different countries. It has been necessary to combine radial velocity measurements from various instruments such as the high-resolution HARPS-N ultrastable spectrograph, installed at the Roque de los Muchachos Observatory's Telescopio Nazionale Galileo (TNG); the CARMENES high resolution spectrograph, installed at the Calar Alto observatory; the HERMES spectrograph, installed on the Mercator telescope, also at the ORM; and the SES spectrograph, installed in the STELLA telescope at the Teide Observatory. Observations taken from the Las Cumbres Observatory, a network of telescopes located around the world, have been used to continuously monitor the variations of the star's activity.

Read more at Science Daily

Mars: Simulations of early impacts produce a mixed Mars mantle

Mars

The early solar system was a chaotic place, with evidence indicating that Mars was likely struck by planetesimals, small protoplanets up to 1,200 miles in diameter, early in its history. Southwest Research Institute scientists modeled the mixing of materials associated with these impacts, revealing that the Red Planet may have formed over a longer timescale than previously thought.

An important open issue in planetary science is to determine how Mars formed and to what extent its early evolution was affected by collisions. This question is difficult to answer given that billions of years of history have steadily erased evidence of early impact events. Luckily, some of this evolution is recorded in Martian meteorites. Of approximately 61,000 meteorites found on Earth, just 200 or so are thought to be of Martian origin, ejected from the Red Planet by more recent collisions.

These meteorites exhibit large variations in iron-loving elements such as tungsten and platinum, which have a moderate to high affinity for iron. These elements tend to migrate from a planet's mantle and into its central iron core during formation. Evidence of these elements in the Martian mantle as sampled by meteorites are important because they indicate that Mars was bombarded by planetesimals sometime after its primary core formation ended. Studying isotopes of particular elements produced locally in the mantle via radioactive decay processes helps scientists understand when planet formation was complete.

"We knew Mars received elements such as platinum and gold from early, large collisions. To investigate this process, we performed smoothed-particle hydrodynamics impact simulations," said SwRI's Dr. Simone Marchi, lead author of a Science Advances paper outlining these results. "Based on our model, early collisions produce a heterogeneous, marble-cake-like Martian mantle. These results suggest that the prevailing view of Mars formation may be biased by the limited number of meteorites available for study."

Based on the ratio of tungsten isotopes in Martian meteorites, it has been argued that Mars grew rapidly within about 2-4 million years after the Solar System started to form. However, large, early collisions could have altered the tungsten isotopic balance, which could support a Mars formation timescale of up to 20 million years, as shown by the new model.

"Collisions by projectiles large enough to have their own cores and mantles could result in a heterogeneous mixture of those materials in the early Martian mantle," said co-author Dr. Robin Canup, assistant vice president of SwRI's Space Science and Engineering Division. "This can lead to different interpretations on the timing of Mars' formation than those that assume that all projectiles are small and homogenous."

The Martian meteorites that landed on Earth probably originated from just a few localities around the planet. The new research shows that the Martian mantle could have received varying additions of projectile materials, leading to variable concentrations of iron-loving elements. The next generation of Mars missions, including plans to return samples to Earth, will provide new information to better understand the variability of iron-loving elements in Martian rocks and the early evolution of the Red Planet.

Read more at Science Daily

'Cataclysmic' collision shaped Uranus' evolution

The collision with Uranus of a massive object twice the size of Earth that caused the planet's unusual spin, from a high-resolution simulation using over ten million particles, coloured by their internal energy.

Uranus was hit by a massive object roughly twice the size of Earth that caused the planet to tilt and could explain its freezing temperatures, according to new research.

Astronomers at Durham University, UK, led an international team of experts to investigate how Uranus came to be tilted on its side and what consequences a giant impact would have had on the planet's evolution.

The team ran the first high-resolution computer simulations of different massive collisions with the ice giant to try to work out how the planet evolved.

The research confirms a previous study which said that Uranus' tilted position was caused by a collision with a massive object -- most likely a young proto-planet made of rock and ice -- during the formation of the solar system about 4 billion years ago.

The simulations also suggested that debris from the impactor could form a thin shell near the edge of the planet's ice layer and trap the heat emanating from Uranus' core. The trapping of this internal heat could in part help explain Uranus' extremely cold temperature of the planet's outer atmosphere (-216 degrees Celsius, -357 degrees Fahrenheit), the researchers said.

The findings are published in The Astrophysical Journal.

Lead author Jacob Kegerreis, PhD researcher in Durham University's Institute for Computational Cosmology, said: "Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system. This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.

"We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet's evolution.

"Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today."

There has been a question mark over how Uranus managed to retain its atmosphere when a violent collision might have been expected to send it hurtling into space.

According to the simulations, this can most likely be explained by the impact object striking a grazing blow on the planet. The collision was strong enough to affect Uranus' tilt, but the planet was able to retain the majority of its atmosphere.

The research could also help explain the formation of Uranus' rings and moons, with the simulations suggesting the impact could jettison rock and ice into orbit around the planet. This rock and ice could have then clumped together to form the planet's inner satellites and perhaps altered the rotation of any pre-existing moons already orbiting Uranus.

The simulations show that the impact could have created molten ice and lopsided lumps of rock inside the planet. This could help explain Uranus' tilted and off-centre magnetic field.

Uranus is similar to the most common type of exoplanets -- planets found outside of our solar system -- and the researchers hope their findings will help explain how these planets evolved and understand more about their chemical composition.

Co-author Dr Luis Teodoro, of the BAER/NASA Ames Research Center, said: "All the evidence points to giant impacts being frequent during planet formation, and with this kind of research we are now gaining more insight into their effect on potentially habitable exoplanets."

Read more at Science Daily

Challenging our understanding of how platelets are made

Platelets are uniquely mammalian cells, and are the small cells of the blood that are critical for us to stop bleeding when we cut ourselves. They are also a central part of the process of thrombosis, which underlies heart attacks and stroke, and form the target of major drugs used in the treatment of these diseases, such as aspirin. These cells are formed from large precursor cells, megakaryocytes, in the bone marrow and the lung, at a remarkable rate of 100 billion platelets per day in adult humans (that is one million platelets per second).

Despite this hugely active process, we still do not understand the details of how platelets are formed in the body. Dysfunction in the process underlies many cases of low platelet count and associated bleeding disorders, and so understanding the process better is essential in order to improve the healthcare we can offer to those affected.

The study 'Multiple membrane extrusion sites drive megakaryocyte migration into bone marrow blood vessels' has been published in the new journal Life Science Alliance (jointly published by EMBO, Cold Spring Harbor Press and Rockefeller Press). It is a collaboration between researchers at the University of Bristol, Imperial College London, the Francis Crick Institute, the University of Glasgow, the University of Oxford and MRC Weatherall Institute of Molecular Medicine. It details how researchers have used a novel approach to visualize the process in vivo, called intravital correlative light-electron microscopy.

Professor Alastair Poole, from the University of Bristol, who contributed to the research said; "The results have allowed us to propose a new mechanism for platelet production. In contrast to current understanding we found that most megakaryocytes enter the sinusoidal space as large protrusions, rather than extruding fine proplatelet extensions (as is currently thought)."

The research highlights this difference is important because the mechanism for large protrusion differs from that of proplatelet extension. Proplatelets extend by the sliding of dense bundles of microtubules, whereas the detailed in vivo data shows an absence of these bundles, but the presence of multiple fusion points between the internal membrane and the plasma membrane, at the leading edge of the protruding cell. Mass membrane extrusion therefore drives megakaryocyte large protrusions into the blood vessels of the bone marrow, significantly revising our understanding of the fundamental biology of platelet formation in vivo.

Read more at Science Daily

Meteorite Strikes Greatly Influenced the Early Composition of Earth and Mars

Meteorites striking Earth have played an integral part in the planet's evolution.

Researchers looking at Earth’s growth as a planet in the early solar system have uncovered a new chaotic twist: planetary bodies like ours gained and lost a “vapor envelope” that caused our planet’s composition to change drastically. This envelope resulted after collisions with small bodies that created a temporary atmosphere of vaporized rock.

Prevailing theory holds that planets grow by accretion, which means gradually gathering gas and dust over time. This sometimes also includes collisions with smaller neighbors. A famous example of the latter was Earth’s long-ago collision with a Mars-sized body; the debris from the crash eventually created the Earth’s moon.

The new research, which was recently published in the journal Nature, shows that the larger bodies that struck Earth and Mars — traveling at several miles a second — created a lot of heat that generated magma oceans, and the temporary vaporized-rock atmosphere. However, Earth as a young planet (when it was smaller than Mars) was too small to have enough gravitational attraction to hold on to this atmosphere, so it eventually bled into space.

Over time, the researchers said, these collisions, and the gain and loss of temporary atmospheres, greatly altered the makeup of Earth and Mars. The evidence is based on looking at samples from Earth rocks, as well as meteorites from Mars and the asteroid Vesta.

“We have provided evidence that such a sequence of events occurred in the formation of the Earth and Mars, using high precision measurements of their magnesium isotope compositions,” said Remco Hin, a senior research associate with the University of Bristol’s school of Earth sciences in a statement.

Isotopes are different forms of an element. In this case, the element studied was magnesium.

“Magnesium isotope ratios change as a result of silicate vapour loss, which preferentially contains the lighter isotopes,” Hin went on. “In this way, we estimated that more than 40 per cent of the Earth’s mass was lost during its construction. This cowboy building job, as one of my co-authors described it, was also responsible for creating the Earth’s unique composition.”

Researchers carried out the work to add weight to a lengthy debate about why planets have poor volatile compositions — a “volatile” is a chemical element or chemical compound with a low boiling point, such as helium. The debate has two main points: the volatiles were lost either because of planetary growth, or due to some process related to the gas and dust environment in which planets in the solar system were born.

Read more at Seeker

Gigantic Jupiter-type planet reveals insights into how planets evolve

An image of the HD 106906 stellar debris disk, created by Erika Nesvold's simulation, showing the ring of rocky and icy planet-forming material rotating around the star. (The star is removed from the image, masked by the black circle.) The different hues represent gradients of brightness in the disk material; yellow is the brightest and blue the dimmest.

An enormous young planet approximately 300 light-years from Earth has given astrophysicists a rare glimpse into planetary evolution.

The planet, known as HD 106906b, was discovered in 2014 by a team of scientists from the U.S., the Netherlands and Italy. It is 11 times the mass of Jupiter and is extremely young by celestial standards -- not more than 13 million years old, compared with our solar system's 4.6 billion years.

"This is such a young star; we have a snapshot of a baby star that just formed its planetary system -- a rare peek at the final stage of planet formation," said Smadar Naoz, a UCLA assistant professor of physics and astronomy, and a co-author of the study.

Another of the planet's unusual characteristics is its distance from its star. Astronomers believe that the vast majority of planets outside of our solar system exist inside a vast dusty disk of debris relatively close to the center of the solar system. But HD 106906b is far beyond its solar system's disk -- so far away that it takes 1,500 years for the planet to orbit its star. HD 106906b is currently at least 650 times as far from its star as the Earth is from our sun.

"Our current planet formation theories do not account for a planet beyond its debris disk," Naoz said.

The study's lead author is Erika Nesvold, a postdoctoral fellow at the Carnegie Institution for Science whom Naoz mentors. She wrote software called Superparticle-Method Algorithm for Collisions in Kuiper belts and debris disks, or SMACK, that allowed the researchers to create a model of the planet's orbital path -- a critical step because HD 106906b orbits so slowly that the researchers can barely see it move.

The research, published online in the Astrophysical Journal Letters, suggests that the planet formed outside the disk, where it's visible it today, as opposed to having been formed inside the debris disk and then having been thrust far beyond it.

Naoz said that conclusion helps explain the shape of the debris disk. "It works perfectly," she said.

The planet's orbit is elliptical; it gets much closer to the star on one side of its orbit than on the other side. And its gravity produces an elliptical shape in the disk as well. One side of the disk is closer to the star than the other side, and the dust on that side is warmer and glows brighter as a result.

The debris disk was photographed in 2016 by American and European astronomers. According to Naoz, the disk is an analog to our solar system's Kuiper belt -- an enormous cluster of small bodies like comets and minor planets located beyond Neptune.

The researchers don't know if there are additional planets inside the disk, but using Nesvold's software -- which also been used to study other debris disks in the universe -- they were able to re-create the shape of the disk without adding another planet into the model, as some astronomers had thought would be required.

Debris disks are composed of gas, dust and ice, and they play a key role in the formation of planets. Typically, Naoz said, planets form after a gas cloud collapses due to its own gravity, forming a disk -- where planets are created -- and a star. As the gas slowly evaporates, the dust and debris rotate and collide around the young star until gravity pushes them away, forming a structure like our solar system's Kuiper belt.

"In our solar system, we've had billions of years of evolution," said Michael Fitzgerald, UCLA associate professor of physics and astronomy, and the study's other co-author. "We're seeing this young system revealed to us before it has had a chance to dynamically mature."

Naoz said the researchers' conclusions do not require any exotic physics or hidden planets to explain them, which is not always the case in studying other solar systems.

Read more at Science Daily

Meteorite Reveals Mars Had Active Volcanoes Two Billion Years Ago

A new analysis of a half-pound meteorite from Mars shows that the Red Planet was volcanically active as far back as two billion years ago, making Mars home to not only the biggest volcanoes in the solar system, but the most long-lived ones as well.

The meteorite, known as Northwest Africa (NWA) 7635, was found in 2012 in Algeria (pictured above). A new isotopic analysis, headed by University of Houston geologist Tom Lapen, ties NWA 7635 with 10 other Martian meteorites that likely were blasted out from the same volcano or lava plain by an impacting asteroid or comet about 1.1 million years ago.

"We don't know exactly where these stones were launched from, but it is likely that they are from the volcanic plains and shield volcanoes of the Tharsis or Elysium regions on Mars," Lapen told Seeker.

The study also showed that NWA 7635's solidified lava dates back 2.4 billion years, far older than similar meteorites (known by their scientific designation as incompatible trace element (ITE) depleted shergottites.)

The previously analyzed meteorites range in age from 327 million years old to 600 million years old, the study shows.

"The discovery of a single Mars ejection site with over 2 billion years of stacked lava flows is critical for understanding the volcanic history of Mars," Lapen said. "These data are exciting because this is the first direct evidence for the absolute timing, mantle source characteristics, and spatial associations of volcanism on Mars."

The research also "sets a template for further testable hypotheses regarding the periodicity of magmatism, timing of volcanic gas fluxes into the atmosphere, and the nature of mantle dynamics over most of Mars' history," he added.

The analysis confirms that some of the oldest volcanoes in the solar system are located on Mars.

Mars already was known to host the largest known volcano in the solar system, Olympus Mons, which is as wide as the state of Arizona and about 16 miles high, according to NASA.

NWA 7635 is among about 124 meteorites from Mars that have been recovered on Earth, NASA's Mars Meteorite website shows.

Lapen's research appears in this week's Science Advances.

From Discovery News