Gizmorama - April 23, 2018
Scientists have discovered a way to replicate the core of exoplanets in the hopes of studying structural pressure and conditions...and lasers are involved! It's the second story.
Learn about this and more interesting stories from the scientific community in today's issue.
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*-- Plants fix UV damage to DNA with robust repair system --*
Scientists have detailed the ability of plants to repair DNA damaged by the sun's ultraviolet rays.
The new study, published this week in the journal Nature Communications, marks the first time scientists have mapped the "nucleotide excision repair" system inside an entire multicellular organism.
The newly mapped system is similar to DNA repair systems found in humans and other animals but is more efficient at repairing active genes.
"These findings advance our understanding of DNA repair mechanisms common among all organisms and may also have practical applications," Ogun Adebali, a postdoctoral researcher at the University of North Carolina, said in a news release.
Unlike humans, plants can't put on sunscreen or take refuge inside. Plus, they need significant amounts of sun to survive -- so they can't avoid DNA damage caused by exposure to the sun's ultraviolet rays. Thus, they require a robust DNA repair system.
The study was made possible by a new analysis technique that allows researchers to sequence the small strands of damaged DNA removed from plant chromosomes during the excision repair process. Scientists can reference the snippets against a healthy plant genome to determine which sections of DNA are under repair.
Scientists used their analysis technique, XR-seq, to identify DNA repair activities happening inside a small, flowering plant called thale cress, Arabidopsis thaliana. The thale cress was exposed to UV radiation inside the lab.
The analysis showed DNA repair happens more efficiently for active genes -- DNA sequences that are actively being translated into RNA and triggering the production of proteins. So-called transcription-coupled repair has previously been documented in mammals and bacteria.
"Here we found that the jump in efficiency for transcription-coupled repair is even more pronounced in plants than it is in animals or bacteria," said postdoctoral researcher Onur Oztas.
When researchers left thale cress samples in the dark, they observed continued DNA-repair activities.
"This implies that excision repair is needed to fix DNA damage from other, unknown factors besides UV," Oztas said. "We'd like to identify and characterize those unknown factors and find out how excision repair fixes the types of damage they cause."
*-- Scientists blast iron with lasers to study the cores of rocky exoplanets --*
By blasting a small iron sample with high-powered lasers at the Lawrence Livermore National Laboratory, scientists can replicate the extreme pressure and density conditions found inside the cores of large, rocky exoplanets.
The experiments have offered scientists unique insights into the core conditions found inside faraway super-Earths.
"The discovery of large numbers of planets outside our solar system has been one of the most exciting scientific discoveries of this generation," Ray Smith, a physicist at LLNL, said in a news release. "These discoveries raise fundamental questions."
"What are the different types of extrasolar planets and how do they form and evolve?" Smith said. "Which of these objects can potentially sustain surface conditions suitable for life? To address such questions, it is necessary to understand the composition and interior structure of these objects."
Of the more than 4,000 confirmed and candidate exoplanets discovered by Kepler and other planet-hunters, the largest percentage are so-called super-Earths, rocky planets with a radius between and one and four times that of Earth.
"Determining the interior structure and composition of these super-Earth planets is challenging but is crucial to understanding the diversity and evolution of planetary systems within our galaxy," Smith said.
The larger the rocky exoplanet, the more intense the pressure found inside its core. Because iron is the most abundant compositional element inside super-Earths, scientists set out to study its properties under extreme pressure.
Scientists used high-powered lasers and ramp compression techniques to replicate the extreme conditions. The laser at LLNL's National Ignition Facility can deliver 2 megajoules of laser energy over 30 nanoseconds, enough to compress the iron sample to 1.4 TPa, with a single TPa equaling 10 million atmospheres. That is four times the pressure achieved during previous experiments and the equivalent of the pressure found inside a rocky exoplanet with three to four times the mass of Earth.
Researchers described the experiments this week in the journal Nature Astronomy.
"Planetary interior models, which rely on a description of constituent materials under extreme pressures, are commonly based on extrapolations of low-pressure data and produce a wide range of predicated material states," Smith said. "Our experimental data provides a firmer basis for establishing the properties of a super-Earth planet with a pure iron planet."
"Furthermore, our study demonstrates the capability for determination of equations of state and other key thermodynamic properties of planetary core materials at pressures well beyond those of conventional static techniques," he said. "Such information is crucial for advancing our understanding of the structure and dynamics of large rocky exoplanets and their evolution."
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