Tracking down the asteroid that sealed the fate of the dinosaurs

Geoscientists from the University of Cologne have led an international study to determine the origin of the huge piece of rock that hit the Earth around 66 million years ago and permanently changed the climate. The scientists analysed samples of the rock layer that marks the boundary between the Cretaceous and Paleogene periods. This period also saw the last major mass extinction event on Earth, in which around 70 percent of all animal species became extinct. The results of the study published in Science indicate that the asteroid formed outside Jupiter's orbit during the early development of our solar system.

According to a widely accepted theory, the mass extinction at the Cretaceous-Paleogene boundary was triggered by the impact of an asteroid at least 10 kilometres in diameter near Chicxulub on the Yucatán Peninsula in Mexico.

On impact, the asteroid and large quantities of earth rock vaporized.

Fine dust particles spread into the stratosphere and obscured the sun.

This led to dramatic changes in the living conditions on the planet and brought photosynthetic activity to a halt for several years.

The dust particles released by the impact formed a layer of sediment around the entire globe.

This is why the Cretaceous-Paleogene boundary can be identified and sampled in many places on Earth.

It contains high concentrations of platinum-group metals, which come from the asteroid and are otherwise extremely rare in the rock that forms the Earth's crust.

By analysing the isotopic composition of the platinum metal ruthenium in the cleanroom laboratory of the University of Cologne's Institute of Geology and Mineralogy, the scientists discovered that the asteroid originally came from the outer solar system.

"The asteroid's composition is consistent with that of carbonaceous asteroids that formed outside of Jupiter's orbit during the formation of the solar system," said Dr Mario Fischer-Gödde, first author of the study.

The ruthenium isotope compositions were also determined for other craters and impact structures of different ages on Earth for comparison. This data shows that within the last 500 million years, almost exclusively fragments of S-type asteroids have hit the Earth. In contrast to the impact at the Cretaceous-Paleogene boundary, these asteroids originate from the inner solar system. Well over 80 percent of all asteroid fragments that hit the Earth in the form of meteorites come from the inner solar system. Professor Dr Carsten Münker, co-author of the study, added: "We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in geological time. The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system."

Read more at Science Daily

Plot thickens in hunt for ninth planet

A pair of theoretical physicists are reporting that the same observations inspiring the hunt for a ninth planet might instead be evidence within the solar system of a modified law of gravity originally developed to understand the rotation of galaxies.

Researchers Harsh Mathur, a professor of physics at Case Western Reserve University, and Katherine Brown, an associate professor of physics at Hamilton College, made the assertion after studying the effect the Milky Way galaxy would have on objects in the outer solar system -- if the laws of gravity were governed by a theory known as Modified Newtonian Dynamics (or MOND).

MOND proposes Isaac Newton's famous law of gravity is valid up to a point. That is, when the gravitational acceleration predicted by Newton's law becomes small enough, MOND allows for a different gravitational behavior to take over.

The observational success of MOND on galactic scales is why some scientists consider it an alternative to "dark matter," the term physicists use to describe a hypothesized form of matter that would have gravitational effects but not emit any light.

"MOND is really good at explaining galactic-scale observations," Mathur said, "but I hadn't expected that it would have noticeable effects on the outer solar system."

Their work was recently published in The Astronomical Journal.

A 'striking' alignment

Mathur and Brown had studied MOND's effect on galactic dynamics before. But they became interested in MOND's more local effects after astronomers announced in 2016 that a handful of objects in the outer solar system showed orbital anomalies that could be explained by a ninth planet.

Orbital peculiarities have led to historic discoveries before: Neptune was discovered through its gravitational tug on the orbits of nearby object, the minute precession of Mercury provided early evidence in support of Einstein's theory of general relativity, and astronomers have recently used orbital dynamics to infer the presence of a supermassive black hole at the center of our Galaxy.

Brown realized MOND's predictions might be at odds with the observations that had motivated the search for a ninth planet. "We wanted to see if the data that support the Planet Nine hypothesis would effectively rule out MOND," she said.

Instead, Mathur and Brown found MOND predicts precisely clustering that astronomers have observed. Over millions of years, they argue, the orbits of some objects in the outer solar system would be dragged into alignment with the galaxy's own gravitational field.

When they plotted the orbits of the objects from the Planet Nine dataset against the galaxy's own gravitational field, "the alignment was striking," Mathur said.

The authors caution that the current dataset is small and that that any number of other possibilities might prove to be correct; other astronomers have argued the orbital peculiarities are the result of observational bias, for example.

Read more at Science Daily

New small laser device can help detect signs of life on other planets

As space missions delve deeper into the outer solar system, the need for more compact, resource-conserving and accurate analytical tools has become increasingly critical -- especially as the hunt for extraterrestrial life and habitable planets or moons continues.

A University of Maryland-led team developed a new instrument specifically tailored to the needs of NASA space missions. Their mini laser-sourced analyzer is significantly smaller and more resource efficient than its predecessors -- all without compromising the quality of its ability to analyze planetary material samples and potential biological activity onsite. The team's paper on this new device was published in the journal Nature Astronomy on January 16, 2023.

Weighing only about 17 pounds, the instrument is a physically scaled-down combination of two important tools for detecting signs of life and identifying compositions of materials: a pulsed ultraviolet laser that removes small amounts of material from a planetary sample and an OrbitrapTM analyzer that delivers high-resolution data about the chemistry of the examined materials.

"The Orbitrap was originally built for commercial use," explained Ricardo Arevalo, lead author of the paper and an associate professor of geology at UMD. "You can find them in the labs of pharmaceutical, medical and proteomic industries. The one in my own lab is just under 400 pounds, so they're quite large, and it took us eight years to make a prototype that could be used efficiently in space -- significantly smaller and less resource-intensive, but still capable of cutting-edge science."

The team's new gadget shrinks down the original Orbitrap while pairing it with laser desorption mass spectrometry (LDMS) -- techniques that have yet to be applied in an extraterrestrial planetary environment. The new device boasts the same benefits as its larger predecessors but is streamlined for space exploration and onsite planetary material analysis, according to Arevalo.

Thanks to its diminutive mass and minimal power requirements, the mini Orbitrap LDMS instrument can be easily stowed away and maintained on space mission payloads. The instrument's analyses of a planetary surface or substance are also far less intrusive and thus much less likely to contaminate or damage a sample than many current methods that attempt to identify unknown compounds.

"The good thing about a laser source is that anything that can be ionized can be analyzed. If we shoot our laser beam at an ice sample, we should be able to characterize the composition of the ice and see biosignatures in it," Arevalo said. "This tool has such a high mass resolution and accuracy that any molecular or chemical structures in a sample become much more identifiable."

The laser component of the mini LDMS Orbitrap also allows researchers access to larger, more complex compounds that are more likely to be associated with biology. Smaller organic compounds like amino acids, for example, are more ambiguous signatures of life forms.

"Amino acids can be produced abiotically, meaning that they're not necessarily proof of life. Meteorites, many of which are chock full of amino acids, can crash onto a planet's surface and deliver abiotic organics to the surface," Arevalo said. "We know now that larger and more complex molecules, like proteins, are more likely to have been created by or associated with living systems. The laser lets us study larger and more complex organics that can reflect higher fidelity biosignatures than smaller, simpler compounds."

For Arevalo and his team, the mini LDMS Orbitrap will offer much-needed insight and flexibility for future ventures into the outer solar system, such as missions focused on life detection objectives (e.g., Enceladus Orbilander) and exploration of the lunar surface (e.g., the NASA Artemis Program). They hope to send their device into space and deploy it on a planetary target of interest within the next few years.

"I view this prototype as a pathfinder for other future LDMS and Orbitrap-based instruments," Arevalo said. "Our mini Orbitrap LDMS instrument has the potential to significantly enhance the way we currently study the geochemistry or astrobiology of a planetary surface."

Read more at Science Daily