A sampling of recent articles, videos, and images from space-related science news items:

** The InSight Mars Lander detects its first Marsquake using the seismometer set on the ground next to the spacecraft:

From NASA:

NASA’s Mars InSight lander has measured and recorded for the first time ever a likely “marsquake.”

The faint seismic signal, detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6, the lander’s 128th Martian day, or sol. This is the first recorded trembling that appears to have come from inside the planet, as opposed to being caused by forces above the surface, such as wind. Scientists still are examining the data to determine the exact cause of the signal.

This image, taken March 19, 2019 by a camera on NASA’s Mars InSight lander, shows the rover’s domed Wind and Thermal Shield, which covers its seismometer, the Seismic Experiment for Interior Structure, and the Martian surface in the background. Credits: NASA/JPL-Caltech

The seismometer signals can be converted to audio:

This video and audio illustrates a seismic event detected by NASA’s Mars InSight rover on April 6, 2019, the 128th Martian day, or sol, of the mission. Three distinct kinds of sounds can be heard, all of them detected as ground vibrations by the spacecraft’s seismometer, called the Seismic Experiment for Interior Structure (SEIS): noise from Martian wind, the seismic event itself, and the spacecraft’s robotic arm as it moves to take pictures. Credits: NASA/JPL-Caltech/CNES/IPGP/Imperial College London.

The new seismic event was too small to provide solid data on the Martian interior, which is one of InSight’s main objectives. The Martian surface is extremely quiet, allowing SEIS, InSight’s specially designed seismometer, to pick up faint rumbles. In contrast, Earth’s surface is quivering constantly from seismic noise created by oceans and weather. An event of this size in Southern California would be lost among dozens of tiny crackles that occur every day.

“The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions,” said Lori Glaze, Planetary Science Division director at NASA Headquarters.

Note that the signals’ frequencies “have been sped up by a factor of 60” since otherwise the vibrations would not be audible to the human ear.

** More quakes in the Cosmos are being detected more quickly with newly upgraded gravity wave observatories in the US and Italy. The sensitivities of the detectors have been increased to a level such that signals picked up at the LIGO (Laser Interferometer Gravitational-Wave Observatory) installations in Louisiana, and Washington plus the European Virgo detector in Italy will result in roughly one gravity wave detection per week. A new public alert system will let everyone know when a detection occurs:

From PSU:

Two new probable gravitational waves — ripples in the fabric of spacetime caused by cataclysmic cosmic events and first predicted by Albert Einstein over 100 years ago — have been detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo observatory in Italy in the first weeks after the detectors were updated. The source of both waves is believed to be the merging of a pair of black holes.

LIGO announced the discovery of the first new gravitational wave in its first-ever open public alert on April 8, and quickly followed up with a second announcement on April 12. LIGO detected the first-ever gravitational wave in September 2015, and announced the discovery in February 2016. Ten more gravitational waves were detected over the following three years, but with updates to LIGO and Virgo, scientists expect to see as many as one per week, which so far has proven true.

Updates to LIGO and Virgo have combined to increase its sensitivity by about 40 percent over its last run. Additionally, with this third observing run, LIGO and Virgo transitioned to a system whereby they alert the astronomy community almost immediately of a potential gravitational wave detection. This allows electromagnetic telescopes (X-ray, UV, optical, radio) to search for and hopefully find an electromagnetic signal from the same source, which can be key to understanding the dynamics of the event.

“The region of sky believed to contain the source of the gravitational wave detected on April 8, 2019. The area spans 387 square degrees, equivalent to nearly 2000 full-Moons, roughly meandering through the constellations Cassiopeia, Lacerta, Andromeda, and Cepheus in the northern hemisphere. IMAGE: LIGO/Caltech/MIT”

… The source of both gravitational waves is suspected to be compact binary mergers — the collision of two massive and incredibly dense cosmic objects into one another. Compact binary mergers can occur between two neutron stars, two black holes, or a neutron star and a black hole. Each of these different types of mergers create gravitational waves with strikingly different signals, so the LIGO team can identify the type of event that created the gravitational waves.

** Huge gallery of Rosetta mission images of comet 67P/Churyumov-Gerasimenko is now available on line at the OSIRIS Image Archive:

The ESA release says the image shown below

… was taken on 6 October 2014 from a distance of 18.6 km to the comet. This is just one of almost 70 000 images taken with Rosetta’s high-resolution imaging system OSIRIS that are now available via a new online and mobile-friendly ‘comet viewer’ created in a joint project with the Department of Information and Communication at Flensburg University of Applied Sciences, and the Max Planck Institute for Solar System Research, who lead the OSIRIS team.

A feature of  Comet 67P/Churyumov-Gerasimenko: “Seen from afar, the comet is usually likened to a duck in shape, but in this enchanting close-up view its profile resembles that of a cat’s face seen side-on. The two ‘ears’ of the cat make up the twin peaks either side of the ‘C. Alexander Gate’ – named for US Rosetta Project Scientist Claudia Alexander who passed away in July 2015. These impressive cliffs lie at the border between the Serqet and Anuket regions on the comet’s head.”

The image viewer hosts the full archive, but also has subsections organising image sets into themes: for example, images showing towering cliffs and bizarre cracks on the comet surface, or those focusing on spectacular dust fountains as the comet launched gas and dust jets into space as its surface ices were warmed as it came closer to the Sun on its orbit.

The collection of OSIRIS images captured the farewell of lander Philae as it dropped towards the surface of the comet, and later, towards the end of the mission, the feverish search for the hidden robot.

Within the new comet viewer, each of the nearly 70 000 images is supplemented with the date on which it was taken, the distance to the comet, and a short accompanying text briefly describing what is seen in the image. The images can be downloaded in full resolution and can also be directly shared to Twitter and Facebook.

** The Southern Crab Nebula shines in a new Hubble image marking 29 years in orbit for the space telescope: Hubble Celebrates its 29th Birthday with Unrivaled View of the Southern Crab Nebula | ESA/Hubble

This incredible image of the hourglass-shaped Southern Crab Nebula was taken to mark the NASA/ESA Hubble Space Telescope’s 29th anniversary in space. The nebula, created by a binary star system, is one of the many objects that Hubble has demystified throughout its productive life. This new image adds to our understanding of the nebula and demonstrates the telescope’s continued capabilities.

The Southern Crab Nebula — Hubble’s 29th anniversary image.

On 24 April 1990, the NASA/ESA Hubble Space Telescope was launched on the space shuttle Discovery. It has since revolutionised how astronomers and the general public see the Universe. The images it provides are spectacular from both a scientific and a purely aesthetic point of view.

Each year the telescope dedicates a small portion of its precious observing time to take a special anniversary image, focused on capturing particularly beautiful and meaningful objects. This year’s image is the Southern Crab Nebula, and it is no exception [1].

This peculiar nebula, which exhibits nested hourglass-shaped structures, has been created by the interaction between a pair of stars at its centre. The unequal pair consists of a red giant and a white dwarf. The red giant is shedding its outer layers in the last phase of its life before it too lives out its final years as a white dwarf. Some of the red giant’s ejected material is attracted by the gravity of its companion.

More highlights from Hubble’s 29 years in orbit:

** Latest Mars updates from Bob Zimmerman:

Comparison of an area near Olympus Mars before (left) and after (right) the global dust storm of 2018. Credits: Bob Zimmerman & HiRISE camera on NASA Mars Reconnaissance Orbiter (MRO)

White streaks atop avalanche debris on this Mars slope appear to be water frost. Credits: Bob Zimmerman + HiRISE camera on NASA Mars Reconnaissance Orbiter (MRO)

Check out a new MRO avalanche image released today by NASA: Landslides in Mars’ Cerberus Fossae | NASA.

The Mast Camera, or Mastcam, on NASA’s Curiosity Mars rover captured this image after “it drilled a rock nicknamed “Aberlady,” on Saturday, April 6, 2019 (the 2,370th Martian day, or sol, of the mission). The rock and others nearby appear to have moved when the drill was retracted. This was the first time Curiosity has drilled in the long-awaited “clay-bearing unit.” See also a GIF animation showing before and after the drilling. Credits: NASA JPL

  • How fast do things change on Mars? – A comparison of Mars Reconnaissance Orbiter images of a dune-like feature on Mars taken 12 years apart show some differences. “Overall, however, not much is different. Though dunes definitely change on Mars, they do so much more slowly than on Earth. And in some cases what look like dunes are not really dunes at all, but a form of cemented sandstone, exhibiting even fewer changes over long time spans.”

** Some space sciences webcasts:

>> Weekly Space Hangout: Apr 17, 2019 – Dr. Dorothy Oehler Talks “Is there Methane on Mars?”

>> SETI Institute: Tiny Neptune Moon Spotted by Hubble May Have Broken from Larger Moon

>> SETI Institute: Mars Exploration Rovers: Spirit and Opportunity with Nathalie Cabrol

>> SETI Institute: Turkish Meteorite Traced to Impact Crater on Asteroid Vesta

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