If the public seems more interested in spaceflight as a vehicle for streaming TV dramas, the reality of both the Europa Clipper liftoff and the astounding ‘catch’ of SpaceX’s Starship booster may kindle a bit more interest in exploring nearby space. When I say ‘nearby,’ bear in mind that on this site the term refers to the entire Solar System, as we routinely discuss technologies that may one day make travel to far more distant targets possible. But to get there, we need public engagement, and who could fail to be thrilled by a returning space booster landing as if in a 1950’s SF movie? Europa may itself offer another boost if Europa Clipper’s science return is anything like what it promises to be. Closing to 15 kilometers from the surface and making 49 passes over the icy ocean world, the spacecraft may give us further evidence that outer system moons can be venues for life. We also have the European Space Agency’s Jupiter Icy Moons Explorer (JUICE), which will study Europa,...

Evidently discovered by French astronomer Pierre Méchain in 1786, Comet Encke was the first periodic comet to be found after Halley’s Comet. It was named after Johann Franz Encke, who first calculated its orbit. It comes into play this morning because it is considered the source of at least part of the Taurid meteor shower, which is the subject of new work out of the University of Maryland that has implications for our thinking about asteroid and comet mitigation. Image: This is an image of short-period comet Encke obtained by Jim Scotti on 1994 January 5 while using the 0.91-meter Spacewatch Telescope on Kitt Peak. The image is 9.18 arcminutes square with north on the right and east at top. The integration time is 150 seconds. Credit: NASA. The Taurids show up in October and November as Earth encounters this stream of debris in an area of its orbit thought to conceal possibly dangerous asteroids. The American Astronomical Society’s Division of Planetary Sciences annual meeting was...

I’m glad to see the widespread coverage of the DART mission results, both in terms of demonstrating to the public what is possible in terms of asteroid threat mitigation, and also of calming overblown fears that we have too little knowledge of where these objects are located. DART (Double Asteroid Redirection Test) was a surprisingly demonstrative success, shortening the orbit of the satellite asteroid Dimorphos by an unexpectedly large value of 33 minutes. The recoil effect from the ejection of asteroid material, perhaps as high as 0.5% of its total mass, accounts for the result. Watching the ejecta evolve has been fascinating in its own right, as the interactions between the two elements of the binary asteroid come into play along with solar radiation pressure. Asteroids have previously been observed that displayed a sustained tail, as Dimorphos did after impact, and the DART results suggest that the hypothesis of similar impacts on these objects is correct. Thus we learn valuable...

I have further thoughts on 'Stapledon thinking,' as discussed in the last post, but my second piece on the topic isn't ready just yet, and in any case I want to give a quick nod to a topic we looked at a few months back, the discovery and analysis of Near Earth Objects that orbit between the Sun and the orbit of Earth. So far we haven't found many of these 'twilight objects,' but the attempts to find them continue. As witness current work with an exceptional instrument. The Dark Energy Camera is a wide-field CCD imager, mounted on a 4-meter telescope at Cerro Tololo (Chile), that was designed for the Dark Energy Survey. The latter mapped hundreds of millions of galaxies to look for insights into the structure of the cosmos. The DES ended in 2019, but DECam continues to produce data that have helped us find fascinating objects like 2015 TG387, a dwarf planet on an extreme orbit that takes it to aphelion at 1000 AU, with a closest solar approach of 65 AU. DECam has also found 12 new...

Although I had Europa on my mind yesterday, I hadn't thought to find a connection between the icy Jovian moon and the DART mission. Yet it turns out the Double Asteroid Redirection Test imaged Jupiter and Europa in July and August as the spacecraft moved toward yesterday's encounter with the binary asteroid Didymos. Controllers used the spacecraft's DRACO imager (Didymos Reconnaissance and Asteroid Camera for Optical navigation) to examine the visual separation between moon and planet, homing in on variations in the pixel count and intensity as the targets moved across the detector. All this in anticipation of the spacing that would soon be detected between the larger asteroid Didymos and its tiny companion Dimorphos. Says Peter Ericksen, SMART Nav software engineer at APL: "Every time we do one of these tests, we tweak the displays, make them a little bit better and a little bit more responsive to what we will actually be looking for during the real terminal event." Image: This is a...

We have the Zwicky Transient Facility at Palomar Observatory to thank for the detection of the strikingly named 'Ayló'chaxnim (2020 AV2). This is a large near-Earth asteroid with a claim to distinction, being the first NEO found to orbit inside the orbit of Venus. I love to explore the naming of things, and now that we have 'Ayló'chaxnim (2020 AV2), we have to name the category, at least provisionally. The chosen name is Vatira, which in turn is a nod to Atira, a class of asteroids that orbit entirely inside Earth's orbit. Thus Vatira refers to an Atira NEO with orbit interior to Venus. As to the 'Ayló'chaxnim, it's a word from indigenous peoples whose ancestral lands took in the mountainous region where the Palomar Observatory is located. I'm told by the good people at Caltech that the word means something like 'Venus Girl.' On June 7, people of Pauma descent gathered for a ceremony at the observatory, having been asked by the team manning the Zwicky Transient...

It pleases me to learn that Dutch astronomer Jan Oort was among the select group of people who have seen Halley's Comet twice. At the age of 10, he saw it with his father on the shore at Noordwijk, Netherlands. In 1986, he saw it again from an aircraft. What a fine experience that would have been for a man who brought so much to the study of comets, including the idea that the Solar System is surrounded by a massive cloud of such objects in orbits far beyond those of the outer planets. Image: Dutch astronomer Jan Oort, a pioneer in the study of radio astronomy and a major figure in mid-20th Century science. Credit: Wikimedia Commons CC BY-SA 3.0. Halley's Comet is a short-period object, roughly defined as a comet with an orbit of 200 years or less, and thus not a member of the Oort Cloud. But let's linger on it for just a moment. The most famous person associated with two appearances of Halley's Comet is Mark Twain, who was born in 1835 with the comet in the sky, and who sensed that...

What makes the asteroid 16 Psyche interesting is that it may well be the exposed core of a planet from the early days of Solar System formation, a nickel-iron conglomeration that normally would lie well below a surface mantle and crust. It's also an M-class asteroid, a category of which it is the largest known sample. These are mostly made of nickel-iron and thought to be fragmented cores, though many have a composition that has not yet been determined. Image: Deep within the terrestrial planets, including Earth, scientists infer the presence of metallic cores, but these lie unreachably far below the planets' rocky mantles and crusts. Because we cannot see or measure Earth's core directly, asteroid Psyche offers a unique window into the violent history of collisions and accretion that created the terrestrial planets. Credit: University of Arizona. M-class asteroids have been imaged before -- the Rosetta spacecraft imaged the non-metallic 21 Lutetia in 2010, and 216 Kleopatra has been...

A century ago, when American magazine science fiction was developing, the Solar System seemed a relatively tidy place. At least, it did in comparison to today. The first issue of Hugo Gernsback's Amazing Stories serialized a reprint of Jules Verne's 1877 novel Off on a Comet and, indeed, in those days comets were the objects most likely to move around the system. The asteroids seemed distant in their belt and in stable orbits and there was little else between the planets. There was no Pluto. Today, of course, we seem to have debris everywhere. The main belt asteroids are joined by trojan objects like the large population around Jupiter, and there is another belt of ancient material out beyond Neptune, the Kuiper Belt. In Earth's neighborhood, interesting objects like 2021 PJ1, whose approach to our planet occurred on August 14 at 1.7 million kilometers, remind us that there is a large population of asteroids that move in orbits well inside the main belt, and could conceivably present...

In addition to its sample return mission at asteroid Bennu, OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) has tightened our projections about the object's future trajectory. Although the impact possibility on Earth through the year 2300 is on the order of 1 in 1750 (0.057%), it's an object we want to keep an eye on, because in 2135 Bennu will make a close approach to Earth that could nudge its trajectory in ways that are difficult to anticipate. OSIRIS-REx spent more than two years working near the 500-meter wide asteroid, studying its mass and composition while tracking its spin and orbital trajectory. In terms of the latter, even factors as tiny as the force the spacecraft exerted during its sample collection event in October of 2020, a mere touch-and-go, had to be considered (the study confirms that the effect was negligible). Far more significant is the Yarkovsky effect, which occurs as solar heating eases on the nightside...

An interstellar freebie like 'Oumuamua or 2I/Borisov is priceless. We don't need to travel light years to see it because it comes to us. Although we're expecting to find a lot more such objects as instruments like the Vera Rubin Observatory come online, right now only two are known to have passed through our system. But only slightly less inaccessible places like the Oort Cloud also bring gifts in the form of long-period comets, and I don't want the advent of C/2014 UN271 Bernardinelli-Bernstein to go unnoticed in these pages, given its startling size and already detected activity. Pedro Bernardinelli (University of Pennsylvania), who along with colleague Gary Bernstein discovered the comet, estimates its nucleus as being between 100 and 200 kilometers (62 and 125 miles) long. This dwarfs Hale-Bopp, and Colin Snodgrass (University of Edinburgh) is quoted in the New York Times as saying: "With a reasonable degree of certainty, it's the biggest comet that we've ever seen." The...

Near-Earth Object Surveyor is a proposed space telescope working at infrared wavelengths, an instrument that just completed a successful mission review and now moves on to the next phase of mission development. In NASA parlance, the upcoming Key Decision Point-B moves into Preliminary Design territory. Getting a spacecraft from concept to flight is a long process, but let's back out to the broader picture. Planetary defense is all about finding objects that could impact the Earth with serious consequences. That means setting size targets, and on that score, we're making progress. In 2010, NASA announced that it had identified 90 percent of all Near Earth Objects larger than 1,000 meters. That moved us to the next target, NEOs larger than 140 meters in size, a goal set by the National Aeronautics and Space Administration Act of 2005. JPL now says about 40% of NEOs within this size range have been identified. So with this work in progress, what does NEO Surveyor bring to the table? For...

The beauty of comet 2I/Borisov, the second interstellar object discovered in our Solar System, is that it looks and acts more or less like, well, an interstellar comet, without the puzzling characteristics of its predecessor, the still controversial ‘Oumuamua. 2I/Borisov’s cometary nature is clear in the latest observations from the European Southern Observatory’s Very Large Telescope, data from which also tell us that this is one of the most undisturbed relics of a circumstellar disk ever found. Scientists believe it never passed close to any star before its 2019 passage by the Sun. We don’t know around which star it formed, but Stefano Bagnulo (Armagh Observatory and Planetarium, Northern Ireland), lead author of one of two new papers on the object, says that 2I/Borisov “could represent the first truly pristine comet ever observed.” Bagnulo’s team used the FORS2 instrument on the VLT (FOcal Reducer and low dispersion Spectrograph), an instrument that can take spectra as well as...

Were the rocky worlds of the inner Solar System depleted in carbon as they formed, the so-called 'carbon deficit problem'? There is evidence for a system-wide carbon gradient in that era, which makes for interesting interactions between our Sun's habitable zone and the far reaches of the system, for as the planets gradually cooled, the carbon so necessary for life as we know it would have been available only far from the Sun. How much of a factor were early comets in bringing carbon into the inner system? This question underlies new work by Charles Woodward and colleagues. Woodward (University of Minnesota Twin Cities / Minnesota Institute of Astrophysics) focuses on Comet Catalina, which was discovered in early 2016. He sees carbon in the context of life: "Carbon is key to learning about the origins of life. We're still not sure if Earth could have trapped enough carbon on its own during its formation, so carbon-rich comets could have been an important source delivering this...

Ryugu is classified as a carbonaceous, or C-type asteroid, a class of objects thought to incorporate water-bearing minerals and organic compounds. Carbonaceous chondrites, the dark carbon-bearing meteorites found on Earth, are thought to originate in such asteroids, but it has been difficult if not impossible to determine the source of most individual meteorites. Hence the significance of the Hayabusa2 mission. JAXA's successful foray to Ryugu represents the first time we've been able to examine a sample of a C-type asteroid through direct collection at the site. Ralph Milliken is a planetary scientist at Brown University, where NASA maintains its Reflectance Experiment Laboratory (RELAB). The laboratory expects samples collected at Ryugu to arrive in short order. Milliken is interested in the history of water in the object: "One of the things we're trying to understand is the distribution of water in the early solar system, and how that water may have been delivered to Earth....

With successful operations at Ryugu (Hayabusa2) and Bennu (OSIRIS-REx), asteroid exploration seems to be moving full tilt, with the prospect of surface samples on the way. We can also look ahead to 16 Psyche, the object of interest for a NASA mission planned to launch in 2022, and the Lucy mission to Jupiter's trojan asteroids, with launch now scheduled for 2021. The latest asteroid entry comes in the form of an interesting collaboration between the Japan Aerospace Exploration Agency (JAXA) and the German Aerospace Center (DLR) targeting asteroid 3200 Phaethon, a flyby mission designed to launch no earlier than 2024. DESTINY+ is its name, the acronym standing for Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science (try to say all that quickly before you've had your morning coffee). The agreement for the bilateral mission was signed on November 11 as part of a joint strategy dialogue between the two space agencies. The new...

A spacecraft about the size of an SUV continues operations at an asteroid the size of a mountain. The spacecraft is OSIRIS-REx, the asteroid Bennu, and yesterday’s successful touchdown and sample collection attempt elicits nothing but admiration for the science team that offered up the SUV comparison. They’re collecting materials with a robotic device 321 million kilometers from home. Yesterday’s operations seem to have gone off without a hitch, the only lingering question being whether the sample is sufficient, or whether further sampling in January will be needed. Preliminary data show that today's sample collection event went as planned ? More details to come once all the data from the event are downlinked to Earth. Thanks, everybody, for following along as we journey #ToBennuAndBack!Next stop: Earth 2023! ? pic.twitter.com/fP7xdOEeOs— NASA's OSIRIS-REx (@OSIRISREx) October 20, 2020 If all goes well, we will acquire the largest surface sample from another world since...

OSIRIS-REx, the little spacecraft with the big acronym (standing for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) has been on station for a year and a half at asteroid Bennu, monitoring the unexpected activity that distinguishes the object. Particle ejection from the surface is the subject of a revised special issue of the Journal of Geophysical Research: Planets collecting 10 papers on the matter. Specifically, the spacecraft has found that particles of rock mostly of pebble-size are being ejected repeatedly -- one or two per day -- from the asteroid’s surface, some of them escaping into space, some moving into a temporary orbit, with the rest falling back onto the surface. Just days after entering orbit on December 31 of 2018, OSIRIS-REx began to spot the activity, which the introduction to the special issue refers to as “ongoing mass shedding” involving millimeter- to centimeter-scale particles. What we have on our hands here is an...

The near-Earth asteroid Ryugu is only about a kilometer wide, but it's telling us a good deal about its own history and that of the Solar System itself thanks to the two touchdowns of Hayabusa2, in February and July of 2019. The geological changes so clear on Earth, the bombardments from objects creating craters here and elsewhere, all mark the evolution of large bodies, but the asteroids take us back to the system's earliest days with little change. They're bundles out of the deep freeze of time. Now we wait for the sample return, currently on its way back to Earth, with arrival in December of this year. Aboard will be surface materials collected during both touchdowns, which will complement the data on the chemical and physical composition of the asteroid already gathered. A team led by Tomokatsu Morota (University of Tokyo) has been using Hayabusa2's onboard ONC-W1 and ONC-T imaging instruments to analyze the dusty matter kicked up by the spacecraft's engines during the two...

Asteroid 162173 Ryugu, recently explored in depth by the Hayabusa2 spacecraft, is a C-type asteroid, rich in carbon. About a kilometer in diameter, it is evidently composed of highly porous material, and seems to have been formed by the agglomeration of fragments from a larger parent body that was broken apart by impacts. We learn this from a new paper in Nature that examines the object's high porosity and the significantly low mechanical strength of its rock fragments, which affect how it would act if hitting an atmosphere. Matthias Grott, of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is the principal investigator for MARA, the DLR-built radiometer that flew on board Hayabusa2 and landed aboard the Mobile Asteroid Surface Scout (MASCOT). Says Grott: "The published results are a confirmation of the results from the studies by the DLR radiometer MARA… It has now been shown that the rock analysed by MARA is typical for the entire surface of the...