asteroids Archives - Many Worlds

New Research Finds The Very Early Solar System Went Through an Especially Intense Period of Asteroid Collisions

An artist’s view of the very early solar system, where dust was collecting into small rocks, which smashed into each other and some became larger. The height of the crash-ups took place during a surprisingly short period of time. (Tobias Stierli, flaeck / PlanetS)

In the earliest days of our solar system — before any planets had been cobbled together — the recently formed Sun was circled by cosmic gas and dust. Over time, fragments of rock formed from the dust and many of these orbiting rocks smashed together and some became the gradually larger components of planets-to-be. Others were not part of any planet formation and became asteroids orbiting the Sun, and sometimes falling to Earth as meteorites.

Scientists have found that these asteroids (and their Earth-bound pieces) remained relatively unchanged since their formation billions of years ago.

And so they provide an archive of sorts, in which the conditions of the early solar system are preserved.

Alison Hunt, a planetary scientist at ETH Zurich in Switzerland, led a team that looked at some of that early solar system history and came up with some surprising results.

She and her team at the Swiss National Centre of Competence in Research (NCCR) PlanetS found that almost all of the asteroidal-cores-turned-meteorites they studied had been formed in a short four-million-year period starting almost eight million years the solar system first came into being. A four million-year time span is short in astronomical terms and also unusual in terms of the precision achieved for the dating.

These results, and some inferences about why this period was so chaotic in the early solar system, were reported in Nature Astronomy late last month.

But before we look at why this might have happened, let’s explore a bit about how the team achieved such precise data about when many asteroids were formed.

One of the iron meteorite samples the team analyzed that was, long ago, the core of an asteroid. (Aurelia Meister)

To access this asteroid/meteorite archive, the researchers had to prepare and examine the extraterrestrial material from iron meteorites that had fallen to Earth. Once part of the metallic cores of asteroids, samples from 18 different iron meteorites were used in the analysis.

The researchers first had to dissolve the samples to be able to isolate the elements palladium, silver and platinum — the key to their efforts.

Using a mass spectrometer they measured abundances of different and identifiable isotopes of these elements, and with their results they could put tighter constraints on the timing of events in the early solar system.

Can We Trust a Handful of Grains to Tell Us About the Early Earth? A Look at the Hayabusa2 Asteroid Sample

February 13, 2022 / Elizabeth Tasker / 0 Comments

The Hayabusa2 sample return capsule returning to Earth. The bright streak in the sky is the capsule, shock heated as it enters the Earth’s atmosphere. The bright lights on the ground are buildings. (JAXA)

In the early hours of December 6, 2020, what appeared to be a shooting star blazed across the sky above the Woomera desert in South Australia. The source was the sample return capsule from JAXA’s Hayabusa2 mission, which contained precious material from a near-Earth asteroid known as Ryugu.

Within 60 hours, the capsule had been retrieved and flown to the curation facility at JAXA’s Institute of Space and Astronautical Science in Japan. In vacuum conditions to prevent any trace of contamination, the capsule was opened to reveal over 5 grams of asteroid grains.

This material is expected to have undergone little change since the early days of the solar system some 4.5 billion years ago, and its highly anticipated analysis could provide new information about how the Earth acquired water and organics needed to begin life. The sample is the first ever collected from a carbonaceous (C-type) asteroid, which resemble primitive meteorites found to have a chemical composition close to that of the Sun.

Tet despite a rigorously planned and executed journey of over 5,000 million kilometers to bring back a pristine sample from space, concerns have remained. Chief among these are whether the rocky grains in the sample capsule were typical of the asteroid.

If the Hayabusa2 spacecraft had inadvertently gathered grains from an unusual spot, or if the grains had been altered during the collection and return to Earth, then deductions about the asteroid’s composition–and therefore our solar system’s past–could be wrong.

The sample from asteroid Ryugu (from Yada et al. Nature Astronomy 2021)

The Hayabusa2 team had already gone to rather extreme lengths to mitigate this issue.

In addition to the rapid retrieval operation that ensured that the sample was not contaminated by our planet’s atmosphere, the spacecraft had performed the dangerous landing twice on the surface of asteroid Ryugu to collect samples from two separate sites.

One of these locations was close to where the spacecraft had made an artificial crater, ejecting material from beneath the asteroid’s surface to be gathered during the second collection operation. Rocky grains from below the top layer surface are expected to be particularly pristine, as they have been protected from the bombardment of sunlight, cosmic rays and micrometeorites.… Read more

Metal Mini-Asteroids Detected Passing Near Earth, Offering Potentially Great Science and Maybe Future Mining

November 3, 2021 / Marc Kaufman / 0 Comments

An artist impression of a close flyby of the metal-rich Near-Earth asteroid 1986 DA. Astronomers using the NASA Infrared Telescope Facility have confirmed that the asteroid is made of 85% metal. (Addy Graham/University of Arizona)

Metal asteroids offer something rare in the solar system — the core of a planet without all the rock that normally surrounds it.

Since it is impossible to directly examine a planetary or lunar core if the parent body remains intact, metal-rich asteroids where the upper mantle and crust layers have been lost to a cataclysmic crash offer a potential path to, in effect, peek inside the depths (and deep time) of an object.

The asteroid Psyche is such an object, and that’s why NASA approved a mission to the asteroid that is scheduled to launch next year. Orbiting the sun between Mars and Jupiter in the largest asteroid belt, Psyche appears to be the exposed nickel-iron core of an early planet, and as such reveals the early evolution of our solar system.

But Psyche is not the only metal-rich asteroid known to astronomers, and it certainly is not the closest.

Two much smaller “mini-Pysches” have been detected that are also comprised of iron, nickel, and other metals ranging from platinum to rare earth elements. And these two mini-asteroids — 1986 DA and 2016 ED85 — were recently found to have their spectral signatures are quite similar to asteroid Psyche.

And unlike Psyche, which is between 180 million and 360 million miles away, these mini-Psyches orbit less than twenty million from Earth every 20 to 30 years.

“These kind of metal-rich Near-Earth asteroids are extremely rare,” said Vishnu Reddy of the University of Arizona, and co-author of a recent paper in Planetary Science Journal. “There are some 27,000 known Near-Earth objects, and only these two are metal rich. Of the 1.2 million asteroids that have been identified, only a little over a dozen are in that metal-rich category.”

Reddy has been part of a group researching unusual near-Earth objects since 2005, and so these findings are most rewarding.

“In the years ahead we can study Psyche, a large metal-rich object that is quite far away,” Reddy said. “And now we also know of two much smaller metal-rich objects that are also much, much closer to us.”

Artist’s conception of Psyche, with orbiter spacecraft. The mission, led by Linda Elkins-Tanton at Arizona State University, is scheduled to launch next year.

Japan’s Hayabusa2 Mission Returns to Earth

December 11, 2020 / Elizabeth Tasker / 0 Comments

Fireball created by the Hayabusa2 re-entry capsule as it passes through the Earth’s atmosphere towards the ground (JAXA).

In the mission control room in Japan, all eyes were fixed on one of the large screens that ran along the far wall. The display showed the night sky, with stars twinkling in the blackness. We were waiting for a delivery from space.

Japan’s Hayabusa2 mission launched from the Tanegashima Space Center on December 3, 2014. The spacecraft was headed to asteroid Ryugu, with the intention of studying the tiny world and collecting a sample to return to Earth.

The mission would prove to be an incredible success. Not only did the spacecraft gather two samples from the asteroid, but it was the first mission to deploy autonomous rovers to explore an asteroid’s surface, generate an artificial crater in order to study the asteroid’s structure and collect a sample of the interior, and additionally, deploy a lander to make scientific measurements from the surface itself. The mission finale was to return the samples safely back to Earth on December 6, 2020. The grains in that sample container may hold clues as to how the Earth became habitable.

Ryugu is an example of a C-type or “carbonaceous” asteroid. These asteroids have undergone relatively little change since the start of the solar system, and are thought to contain hydrated minerals (minerals containing water in their structure) and possible organics. It is this class of asteroid that may have crashed into the early Earth and delivered the necessary tools for life to begin. Analysis of the Ryugu sample could therefore tell us about our own beginnings and how terrestrial planets develop habitable conditions.

Images before and after the first touchdown of Hayabusa2 on asteroid Ryugu, taken with CAM-H on February 21, 2019 (animation plays at 5x speed) (JAXA).

As the Hayabusa2 spacecraft drew near the Earth, five “trajectory control manoeuvres” (TCMs) were planned. The first four of these were designed to put the spacecraft onto a collision course with the Earth, aimed at the Woomera desert in Australia. The re-entry capsule would then be released, and the spacecraft would make a final manoeuvre to divert onto an orbit that swept past the Earth and back into deep space.

Despite the smooth progress so far, there were concerns. The capsule release mechanism had not been tested since launch six years previously and it was always possible that separation would fail.… Read more

Cores, Planets and The Mission to Psyche

August 20, 2020 / Marc Kaufman / 0 Comments

The asteroid Psyche will be the first metal-rich celestial body to be visited by a spacecraft. The NASA mission launches in 2022 and is expected to arrive at the asteroid in late 2026. A central question to be answered is whether Psyche is the exposed core of a protoplanet that was stripped of its rocky mantle. (NASA)

Deep inside the rocky planets of our solar system, as well as some solar system moons, is an iron-based core.

Some, such as Earth’s core, have an inner solid phase and outer molten phase, but the solar system cores studied so far are of significantly varied sizes and contain a pretty wide variety of elements alongside the iron. Mercury, for instance, is 85 percent core by volume and made up largely of iron, while our moon’s core is thought to be 20 percent of its volume and is mostly iron with some sulfur and nickel.

Iron cores like our own play a central role in creating a magnetic field around the planet, which in turn holds in the atmosphere and may well be essential to make a planet habitable. They are also key to understanding how planets form after a star is forged and remaining dense gases and dust are kicked out to form a protoplanetary disk, where planets are assembled.

So cores are central to planetary science, and yet they are obviously hard to study. The Earth’s core starts about 1,800 miles below the surface, and the cores of gas giants such as Jupiter are much further inward, and even their elemental makeups are not fully understood.

All this helps explains why the upcoming NASA mission to the asteroid Psyche is being eagerly anticipated, especially by scientists who focus on planetary formation.

Scheduled to launch in 2022, the spacecraft will travel to the main asteroid belt between Mars and Jupiter and home in on what has been described as an unusual “metal body,” which is also one of the largest asteroids orbiting the sun.

While some uncertainty remains, it appears that Psyche is the exposed nickel-iron core of a long-ago emerging rocky protoplanet, with the rest of the planet stripped away by collisions billions of years ago.

An artist’s impression of solar system formation, and the formation of a protoplanetary disk filled with gases and dust that over time clump together and smash into each other to form larger and larger bodies. (Gemini Observatory/AURA artwork by Lynette Cook )

That makes Psyche a most interesting place to visit.… Read more

Hayabusa2 Snatches Second Asteroid Sample

July 18, 2019 / Elizabeth Tasker / 2 Comments

Artist impression of the Hayabusa2 spacecraft touching down on asteroid Ryugu (JAXA / Akihiro Ikeshita)

“1… 2… 3… 4…”

The counting in the Hayabusa2 control room at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Sciences (JAXA, ISAS) took on a rhythmic beat as everyone in the room took up the chant, their eyes fixed on the large display mounted on one wall.

“10… 11… 12… 13…”

The display showed the line-of-sight velocity (speed away from or towards the Earth) of the Hayabusa2 spacecraft. The spacecraft was about 240,000,000 km from the Earth where it was studying a near-Earth asteroid known as Ryugu. At this moment, the spacecraft was dropping to the asteroid surface to collect a sample of the rocky body.

“20… 21… 22… 23…”

Asteroid Ryugu from an altitude of 6km. Image was captured with the Optical Navigation Camera – Telescopic (ONC-T) on July 20, 2018 ( JAXA, University of Tokyo & collaborators)

Asteroid Ryugu is a carbonaceous or “C-type” asteroid; a class of small celestial bodies thought to contain organic material and undergone relatively little alteration since the beginning of the Solar System. Rocks similar to Ryugu would have pelted the early Earth, possibly delivering both water and the first ingredients for life to our young planet. Where and when these asteroids formed and how they moved through the Solar System is therefore a question of paramount importance to understanding how terrestrial planets like the Earth became habitable. It is a question not only tied to our own existence, but also to assessing the prospect of life elsewhere in the Universe.

The Hayabusa2 mission arrived at asteroid Ryugu just over one year ago at the end of June 2018. The spacecraft remotely analyzed the asteroid and deployed two rovers and a lander to explore the surface. Then in February of this year, the spacecraft performed its own descent to touchdown and collect a sample. The material gathered will be analyzed back on Earth when the spacecraft returns home at the end of 2020.

Touchdown is one of the most dangerous operation in the mission. The distances involved mean that it took about 19 minutes to communicate with the spacecraft during the first touchdown and 13 minutes during the second touchdown, when the asteroid had moved slightly closer to Earth. Both these durations are too long to manually guide the spacecraft to the asteroid surface.… Read more

Asteroid Remains Around Dead Stars Reveal the Likely Fate of Our Solar System

June 28, 2018 / Elizabeth Tasker / 0 Comments

Artist concept of an asteroid breaking up. (NASA/JPL-Caltech)

June 30th has been designated “Asteroid Day” to promote awareness of these small members of our solar system. But while asteroids are often discussed in the context of the risk they might pose to the Earth, their chewed up remains around other stars may also reveal the fate of our solar system.

It is 6.5 billion years into our future. The sun has fused hydrogen into a core of heavier helium. Compressed by its own gravity, the helium core releases heat and the sun begins to swell. It is the end of our star’s life, but what will happen to the solar system?

While very massive stars end their element-fusing days in a colossal explosion known as a supernovae, the majority of stars in our galaxy will take a less dramatic exit.

Our sun’s helium core will fuse to form carbon but there is not enough mass to achieve the crushing compression needed for the creation of heavier elements. Instead, the outer layers of the dying star will be blown away to leave a dense remnant with half the mass of our current sun, but squeezed down to the size of the Earth. This is a white dwarf; the most common of all stellar ends.

The life cycle of our sun

The white dwarf rapidly cools to become a dim twinkle in the sky. Within a few million years, our white dwarf will be less luminous that the sun today. Within 100 million years, it will be dimmer by a factor of 100. But examination of white dwarfs in our galaxy reveals this gentle dimming of the lights is not as peaceful as first appears.

The remnants of stars too light to fuse carbon, white dwarfs have atmospheres that should be thin shells of residue hydrogen and helium. Instead, observations have detected 20 different heavy elements in this envelope of gases that include rock-forming elements such as silicon and iron and volatiles such as carbon and nitrogen.

Infrared observations of over forty white dwarfs have additionally revealed compact dusty discs circling the dead stars. Sitting within the radius of a regular star, these could not have formed before the star shrank into a white dwarf. These must be the remains of what occurred as the star morphed from a regular fusion burner into a white dwarf.

This grizzly tale begins with the star’s expansion.… Read more

Primordial Asteroids, And The Stories They Are Telling

August 7, 2017 / Marc Kaufman / 0 Comments

The main asteroid belt of our solar system — with almost two million asteroids a kilometer in diameter orbiting in the region between Mars and Jupiter. There are billions more that are smaller. New research has identified the “family” of a primordial asteroid or planetesimal, one of the oldest ever detected.

Asteroid, we’ve long been told, started tiny in our protoplanetary disk and only very gradually became more massive through a process of accretion. They collected dust from the gas cloud that surrounded our new star, and then grew larger through collisions with other growing asteroids.

But in recent years, a new school of thought has proposed a different scenario: that large clumps of dust and pebbles in the disk could experience gravitational collapse, a binding together of concentrated disk material.

This process would produce a large asteroid (which is sometimes called a planetesimal) relatively quickly, without that long process of accretion. This theory would solve some of the known problems with the gradual accretion method, though it brings some problems of its own.

Now research just published in the journal Science offers some potentially important support to the gravitational collapse model, while also describing the computational detection of a primordial family of asteroids some 4 billion years old.

Led by Marco Delbo’, an astrophysicist at the University of the Côte d’Azur in Nice, France, the scientists have identified a previously unknown family of darkly colored asteroids that is “the oldest known family in the main belt,” their study concluded.

The family was identified and grouped together by the unusual darkness (low albedo) of its asteroids’ reflective powers, a signature that the object has a high concentrations of carbon-based organic compounds. This family of asteroids was also less extensively heated — having formed when the sun radiated less energy — and contains more water, making them potential goldmines for understanding the makeup and processes of the early solar system.

Artist depiction of a dusty disc surrounding a red dwarf.artist rendering of a protoplanetary dust disk, from which asteroid, planetesimals and ultimately planets are formed. NASA/JPL-Caltech/T. Pyle (SSC)

“They are from an original planetesimal and the location of these fragments tell us they are very, very old,” Delbo’ told me. “So old that the original object is older than the epoch when our giant planets moved to their current locations.” That would make this ancient asteroid family more than 4 billion years old, formed when the solar system was but 600 million years from inception.… Read more

Ceres, Asteroids And Us

February 16, 2017 / Marc Kaufman / 0 Comments

Ceres, as imaged by the spacecraft Dawn on a high altitude orbit 900 miles from the surface. The several bright spots on the asteroid have been of particular interest to scientists and are believed to contain salts and ice. The image is mosaic formed from a series of images. (NASA/JPL-Caltech)

For most of us, asteroids exist primarily as a threat. An asteroid that landed around the Yucatan peninsula, after all, is generally considered to have set into motion the changes that resulted in the elimination of the dinosaurs.

Other large in-coming asteroids laid waste to swaths of Siberia in 1908, dug the world’s largest crater (118 mile wide) in South Africa long ago, and formed the Chesapeake Bay a mere 35 million years past. And another large asteroid will almost certainly threaten Earth again some day.

There is, however, a reverse and possibly life-enhancing side to the asteroid story, one that is becoming more clear and intriguing as we learn more about them where they live. Asteroids not only contain a lot of water — some of it possibly delivered long ago to a dry Earth — but they contain some pretty complex organic molecules, the building blocks of life.

The latest chapter in the asteroid saga is being written about Ceres, the largest asteroid in the solar system and recently declared to also be a dwarf planet (like Pluto.)

Using data from NASA’s Dawn spacecraft, a team led by the National Institute for Astrophysics in Rome and the University of California, Los Angeles identified a variety of complex organic compounds, amino acids and nucleobases — the kind that are the building blocks of life. The mission has also detected signs of a possible subsurface ocean as well as cryovolcanos, which spit out ice, water, methane and other gases instead of molten rock.

“This discovery of a locally high concentration of organics is intriguing, with broad implications for the astrobiology community,” said Simone Marchi, a senior research scientist at Southwest Research Institute and one of the authors of the paper in Science. “Ceres has evidence of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and now organic materials.”

He said that the organic-rich areas include carbonates and ammonia-based minerals, which are Ceres’ primary constituents. Their presence along with the organics makes it unlikely that the organics arrived via another asteroid.

In an accompanying comment in the Feb. 16 edition of Science, Michael Küppers of the European Space Astronomy Center in Madrid makes the case that Ceres might once have even been habitable.… Read more

Many Worlds

Tag: asteroids