Wind the cosmic clock back a few billion years and our Solar System looked much different than it does today. About 4.5 billion years ago, the young Sun shone much like it does now, though it was a little smaller. Instead of being surrounded by planets, it was ensconced in a swirling disk of gas and dust. That disk is called a protoplanetary disk and it’s where the planets eventually formed.
There was a conspicuous gap in the early Solar System’s protoplanetary disk, between where Mars and Jupiter are now, and where the modern-day asteroid belt sits. What exactly caused the gap is a mystery, but astronomers think it’s a sign of the processes that governed planet formation.
A group of scientists have published a paper outlining the discovery of this ancient gap. The lead author is Cauê Borlina, a Planetary Science Ph.D. student in the Department of Earth, Atmospheric, and Planetary Sciences (EAPS) at the Massachusetts Institute of Technology (MIT). The title of the paper is “Paleomagnetic evidence for a disk substructure in the early solar system.” It’s published in the journal Science Advances.
Thanks to facilities like the Atacama Large Millimeter/sub-Millimeter Array (ALMA), astronomers are getting better at looking at younger solar systems that still have protoplanetary disks and are still forming planets. They often have conspicuous gaps and rings that are evidence of planets forming. But how exactly it all works is still a mystery.
“Over the last decade, observations have shown that cavities, gaps, and rings are common in disks around other young stars,” says Benjamin Weiss, study co-author and professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “These are important but poorly understood signatures of the physical processes by which gas and dust transform into the young sun and planets.”
This ALMA image of the protoplanetary disk around the nearby young star TW Hydrae reveals the rings and gaps in young disks. Credit: S. Andrews (Harvard-Smithsonian CfA); B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO)
The evidence for a gap in our own Solar System’s protoplanetary disk some 4.5 billion years ago comes from the study of meteorites.
The Solar System’s magnetic fields had an effect on the structure of meteorites. The paleomagnetism shaped the tiny rocks in the protoplanetary disk called chondrules. Chondrules are molten or partially molten pieces of round rock that became accreted to a type of meteorite called chondrites. And chondrites are some of the oldest rocks in the Solar System.
As the chondrules cooled they retained a record of the magnetic fields at the time. Those magnetic fields change over time as the protoplanetary disk evolves. The orientation of the electrons in the chondrules is different depending on the nature of the magnetic fields at the time. Collectively, all those chondrules in all those chondrites tell a tale.
This is an image of a chondrite named NWA 869 (Northwest Africa
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Chinese Astronauts May Build a Base Inside a Lunar Lava Tube
Caves were some of humanity’s first shelters. Who knows what our distant ancestors were thinking as they sought refuge there, huddling and cooking meat over a fire, maybe drawing animals on the walls. Caves protected our ancient ancestors from the elements, and from predators and rivals, back when sticks, stones, furs and fire were our only technologies.
So there’s a poetic parallel between early humans and us. We’re visiting the Moon again, and lunar caves could shelter us the way caves sheltered our ancestors on Earth.
On the Moon, astronauts will need protection from a different set of hazards. They’ll have to contend with cosmic and solar radiation, meteorites, wild temperature swings, and even impact ejecta. The Lunar Reconnaissance Orbiter (LRO) has found hundreds of lunar ‘skylights,’ locations where a lava tube’s ceiling has collapsed, making a natural opening into the tube. It’s hard to tell without exploring, but lava tubes several hundred meters in diameter could exist on the Moon. That’s a lot of room to work with, and they could provide the shelter astronauts will need. The idea is to build a base inside a lunar lava tube, where astronauts gain additional protection from the thick rock ceiling overhead.
China is considering the idea now, just like others before them. Lunar lava caves might be a resource too valuable to ignore.
Lava tubes are also called pyroducts. They formed when lava flowing across the surface of the Moon began to cool. The top of the flowing lava formed a hardened crust, but the molten lava kept flowing underneath it and eventually drained, leaving an empty tube. They’re here on Earth as well.
This is the entrance to a lava tube on Hawaii’s Big Island. Image Credit: By dronepicr – Lava tube Big island Hawaii, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=75616740
Scientists aren’t sure when lunar volcanism ended. It may have been as far back as one billion years ago, though some evidence shows there was small-scale volcanism in the last 50 million years. In either case, these lava tubes are ancient and untouched.
On the Moon, astronauts will have to contend with the temperature swings. Earth’s natural satellite is a world of temperature extremes. One side of the Moon is in direct sunlight for half of the time, and surface temperatures reach as high as 127 Celsius (260 F.) The side that’s shrouded in darkness sinks as low as -173 C (-280 F.) That wild temperature swing makes it challenging to work on the lunar surface, and to engineer and build equipment that can be effective in such a large range. Lava tubes provide a natural steady-temperature environment that can’t be found elsewhere on the Moon.
Radiation is also hazardous on the lunar surface. It can be as much as 150 times more powerful than on Earth’s surface. That’s deadly, but in lunar caves astronauts would be sheltered by several metres of overhead rock. That’s a thick enough barrier to provide effective protection.
The risk of impacts and impact debris is much smaller, but it has to be accounted for. Obviously, lava tubes provide shelter from small impacts.
Different teams of scientists from different countries and agencies have studied the idea of using lava tubes as shelter. At a recent conference in China, Zhang Chongfeng from the Shanghai Academy of Spaceflight Technology presented a study into the underground world of lava tubes. Chinese researchers did fieldwork in Chinese lava tubes to understand how to use them on the Moon.
According to Zhang, there’s enough similarity between lunar and Earthly lava tubes for one to be an analogue of the other. It starts with their two types of entrances, vertical and sloped. Both worlds have both types.
Most of what we’ve found
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Even Tiny Amounts of DNA on Mars Will Be Detectable
The Search for Life is focused on the search for biosignatures. Planetary life leaves a chemical fingerprint on a planet’s atmosphere, and scientists are trying to work out which chemicals in what combinations and amounts are a surefire indicator of life. Martian methane is one they’re puzzling over right now.
But new evidence suggests that super-tiny amounts of DNA can be detected in Martian rocks if it’s there. And though it requires physical samples rather than remote sensing, it’s still an intriguing development.
DNA is the gold standard for biosignatures. “DNA is an incontrovertible biosignature whose sequencing aids in species identification, genome functionality, and evolutionary relationships,” a new paper states. Advances in DNA have led to all kinds of leaps in industry, medicine, paleontology, and even criminal justice. Now, it looks like the search for life might receive similar benefits.
The new paper is “DNA sequencing at the picogram level to investigate life on Mars and Earth.” It’s published in Nature Scientific Reports, and the lead author is Jyothi Basapathi Raghavendra. Raghavendra is a Ph.D. researcher in the Department of Planetary Sciences in the School of Geosciences at the University of Aberdeen.
“There is a slim chance that microbial life exists on Mars today, but to find it, we need to operate at the sample scale, and that’s where the size and power of the hardware that’s used in space exploration is a crucial factor,” said study co-author Javier Martin-Torres.
If this technology can be brought to bear on Martian soil samples, it could be a game-changer.
“Investigating active life forms in extremely low biomass environments is a topic of interest for expanding our knowledge of Earth’s biodiversity and the search for life on Mars,” the authors write.
NASA’s Perseverance rover puts its robotic arm to work around a rocky outcrop called “Skinner Ridge” in Mars’ Jezero Crater. Perseverance gathered an important sample of sedimentary rock here. If there’s any biomass in any of Perseverance’s samples, there will almost certainly be very little of it. But new DNA detection tools could find it. Credit: NASA/JPL-Caltech/ASU/MSSS
Low biomass environments are samples with a very small number of desirable cells. The tiny amount of material makes them more difficult to study, and they present problems to researchers because they’re more easily contaminated. With such a tiny amount of genetic material, it’s also harder to accurately amplify them without errors. “Hence, for the study of low concentrations of DNA, there is a need for new technologies with improved efficiency, sensitivity, and specificity,” the authors write.
The new method is called nanopore technology. A nanopore is simply a really, really tiny hole. Basically, researchers pass an electric current through the nanopore, and if something—a strand of DNA, in this case—passes through the pore, it changes the current. Different changes tell scientists different things about the DNA. Group a couple thousand of these nanopores into one tool, and you’re really onto something.
A company named Oxford Nanopore Technologies developed a tool named MinION to sequence DNA in this way. They say they can sequence any fragment of DNA or RNA from short to ultra-long. They can also do it with as little as two picograms of material. (A picogram is one-trillionth of a gram.) “This result is an excellent advancement in sensitivity, immediately applicable to investigating low biomass samples,” the authors of the study write.
“We aim to push the technology even further for when the Mars Sample Return mission returns in 2033.”
Clive Brown, CTO, Oxford Nanopore
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It’s Official. No More Astronomy at Arecibo
Even though the National Science Foundation announced last year that it would not rebuild or replace the iconic Arecibo radio dish in Puerto Rico — which collapsed in 2020 – a glimmer of hope remained among supporters that the remaining astronomy infrastructure would be utilized in some way.
Instead, the NSF announced this week they have chosen four institutions to transition the site from its historic hub of astronomical research to a STEM educational outreach center, with a seeming focus on biology. A biomedical laboratory, Cold Spring Harbor Laboratory in New York along with the University of Maryland, Baltimore County, and the University of Puerto Rico (UPR) and the University of the Sacred Heart, both in San Juan will oversee the new education center.
NSF said they will invest over $5 million in the site over five years to create the Arecibo Center for Culturally Relevant and Inclusive Science Education, Computational Skills, and Community Engagement (Arecibo C3). According to a press release, NSF said the site “will serve as a catalyst for increased and inclusive engagement in a broad range of science, technology, engineering and mathematics disciplines, cutting-edge research and workforce development initiatives by students, teachers, researchers, local communities and the public within and outside of Puerto Rico.” It is scheduled to open in early 2024.
Previously, before the telescope’s collapse, NSF contributed about $7.5 million annually to the operation of the site.
Arecibo Observatory in its heyday. Credit: NSF.
The Arecibo telescope was a 305 m (1,000 ft) spherical reflector radio telescope built into a natural sinkhole and located near Arecibo, Puerto Rico. It was completed in 1963 and for over 50 years (until the China’s Five-hundred-meter Aperture Spherical Telescope (FAST) was complete in 2016) it was the world’s largest single-aperture telescope. It was used in three major areas of research: radio astronomy, atmospheric science, and radar astronomy.
The facility contributed to significant breakthroughs in astronomy and cosmology, including the discovery of the first binary pulsar, the first-millisecond pulsar, and the first exoplanets, along with helping to study asteroids and planets in the Solar System. In addition, the facility has also played an important role in the Search for Extraterrestrial Intelligence (SETI). The observatory has appeared in movies, television shows and more, and is listed on the US National Register of Historic Places.
Issues for the telescope began in 2017 when Hurricane Maria tore through Puerto Rico, shearing off one of the 29-meter (96-foot) antennas suspended above dish, with falling debris puncturing the dish in several places. In early 2020, earthquakes temporarily closing the observatory for safety reasons; then a succession of cable failures ultimately led to the December 2020 collapse of the 900-ton instrument platform suspended above the observatory, which crashed down on the iconic telescope’s giant dish.
Damage at the Arecibo Observatory in August, 2020. Credit: NSF/NAIC
Since the collapse, many called for the telescope to be rebuilt or for building an even better replacement telescope at the site. A group of astronomers have proposed building a site with 102 13-meter dishes to create a “next generation” Arecibo observatory, arranging them in a fixed circular array 130 meters across. This would be less than half
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