Well That’s Weird…

The South Pole-Aitken basin, the largest crater in the Solar System, is a gigantic impact structure on the far side of the Moon. Data from NASA’s lunar spacecraft points to the existence of a large excess of mass of about 2.18*1018 kg (about five times larger than the Big Island of Hawaii) in the lunar mantle underneath the basin. According to new research, this mass anomaly may contain metal from a massive asteroid that crashed into the Moon and formed the crater.

The South Pole-Aitken basin is oval-shaped, as 1,600 miles (2,500 km) wide and 8.1 miles (13 km) deep. Despite its size, it cannot be seen from Earth because, you know, it is on the far side of the Moon.

Researchers measured and analyzed small changes in the strength of gravity around the Moon, using data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission. When they combined that with lunar topography data from NASA’s Lunar Reconnaissance Orbiter, they discovered the unexpectedly large amount of mass hundreds of miles underneath the South Pole-Aitken basin.

The dense mass, whatever it is, wherever it came from, is weighing the basin floor downward by more than half a mile.

Computer simulations of large asteroid impacts suggest that, under the right conditions, an iron-nickel core of an asteroid may be dispersed into the lunar upper mantle during an impact.

The findings appear in the journal Geophysical Research Letters.

Could Moons Contain Life?

According to new research, exomoons (natural satellites of planets outside our Solar System) could offer another clue about the pool of alien worlds that may be home to life.

Only a small proportion of exoplanets are likely to be able to sustain life, existing in the habitable zone of their stars. But some planets, especially large gas giants, may harbor moons which contain liquid water.

These moons can be internally heated by the gravitational pull of the planet they orbit, which can lead to them having liquid water well outside the normal habitable zones of systems that scientists are trying to find Earth-like planets in.

Researchers looked at the possibility of exomoons orbiting J1407b, a large gas giant believed to have an enormous ring system. J1407b circles a 16-million-year-old Sun-like star approximately 434 light-years away from Earth. The planet’s mass is thought to be in the range of about 10 to 40 Jupiter masses.

The rings of J1407b are shown eclipsing the young Sun-like star J1407. Image credit: Ron Miller.

J1407b

Scientists ran computer simulations to model the rings around J1407b, which are 200 times larger than those around Saturn. Gravitational forces between particles were calculated and used to update the positions, velocities, and accelerations in the computer models of J1407b and its ring system. They then added a moon that orbited at various ratios outside of the rings to test whether this caused gaps to form where they expected.

The findings revealed that while the orbiting moon did have an effect on the scattering of particles along the ring edge, the expected gaps in the ring structure were unlikely to be caused by the gravitational forces of a currently unseen moon orbiting outside J1407b’s rings.

The paper was published in the Monthly Notices of the Royal Astronomical Society.

More T-Rex Cousins

Two new species of predatory megaraptoran dinosaurs have been identified from fossils found in Thailand. The two new species, named Phuwiangvenator yaemniyomi and Vayuraptor nongbualamphuensis, roamed the Earth approximately 125 million years ago (Cretaceous period). The fossilized remains were found in the Sao Khua Formation of Thailand.

Both creatures belong to Megaraptora (megaraptors), a group of medium-to-large-sized theropod dinosaurs. The relatives of this group of predatory dinosaurs include Tyrannosaurus Rex. Like T-Rex, they ran on their hind legs, but the tyrant lizard, their arms were strong and armed with long claws. They also had more delicate heads that ended in a long snout.

Phuwiangvenator yaemniyomi was likely a fast runner. At about 20 feet (6 m) long, this dinosaur was considerably smaller than T-Rex which was approximately 40 feet (12 m) in length. Vayuraptor nongbualamphuenisis measured approximately 15 feet (4.5 m) long.

Scientists have compared the Thai fossils with other megaraptors discovered in South America and Australia. Various characteristics of Phuwiangvenator yaemniyomi indicate that it is an early representative of the group. This is an indication that the megaraptors originated in Southeast Asia and then spread to other regions.

The study was published in the journal Acta Palaeontologica Polonica.

New Neighbors

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Astronomers using NASA’s Transiting Exoplanets Survey Satellite (TESS) have discovered a compact three-planet system around the star HR 858. The newly-discovered planets orbit HR 858, a slightly-evolved F-type star, which is also a member of a visual binary system. The star lies in the constellation of Fornax, approximately 104.4 light-years from Earth. It has a radius 30% larger than the Sun, and a temperature of about 10,700 degrees Fahrenheit (5,928 degrees Celsius).

Named HR 858b, c and d, the new planets are all about twice the size of Earth and have periods of 3.6, 6 and 11.2 days, respectively. This compact and near-resonant architecture harkens back to the systems of tightly packed inner planets discovered by Kepler, but HR 858 is hundreds to thousands of times brighter than the hosts of those Kepler systems.

According to the team, HR 858 is one of the brightest stars known to host transiting exoplanets, trailing only HD 219134, pi Mensae, and 55 Cancri.

Pre-launch estimates of the TESS planet yield predicted a handful of planet discoveries around naked-eye stars, and so far only HR 858 and pi Mensae have fit this description. HR 858 will likely retain its privileged position as one of the brightest transit hosts in the sky and most favorable systems for detailed study.

paper detailing the discovery will be published in a journal of the American Astronomical Society (AAS).

Ice, Ice, Baby

 

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Planetary researchers using data from the Shallow Radar (SHARAD) instrument on NASA’s Mars Reconnaissance Orbiter have discovered rich deposits of water ice and sand hundreds of million years old beneath the current ice cap in the north polar region of the Red Planet. Published journal Geophysical Research Letters, the findings are important because the layers of ice are a record of past Martian climate in much the same way that tree rings are a record of past climate on Earth.

Scientists found layers of sand and ice that were as much as 90% water in some places. If melted, the newly-discovered ice would be equivalent to a global layer of water around Mars at least 5 feet (1.5 m) deep, which could be one of the largest water reservoirs on the planet.

The scientists suspect the layers formed when ice accumulated at the poles during past ice ages on Mars. Each time the planet warmed, a remnant of the ice caps became covered by sand, which protected the ice from solar radiation and prevented it from dissipating into the atmosphere.

Until now, scientists thought the ancient ice caps were lost. The new findings show that in fact significant ice sheet remnants have survived under the planet’s surface, trapped in alternating bands of ice and sand, like layers on a cake.

The total volume of water locked up in the buried polar deposits is roughly the same as all the water ice known to exist in glaciers and buried ice layers at lower latitudes on Mars, and they are approximately the same age.

The team’s findings were corroborated by an independent study using gravity data instead of radar, led by Johns Hopkins University’s Dr. Lujendra Ojha and also published in the journal Geophysical Research Letters.