In a recent study submitted to Earth and Planetary Astrophysics, a team of researchers from Yale University investigated how to identify impact craters that may have been created by Interstellar Objects (ISOs). This study is intriguing as the examination of ISOs has gained notable interest throughout the scientific community since the discoveries and subsequent research of ‘Oumuamua and Comet 2I/Borisov in 2017 and 2019, respectively. In their paper, the Yale researchers discussed how the volume of impact melt within fixed-diameter craters could be a possible pathway for recognizing ISO craters, as higher velocity impacts produce greater volumes of impact melt.
The Moon contains more metal than previously thought, according to a new study. Is it time to re-think the giant impact hypothesis? Image Credit: NASA / GSFC / Arizona State University
Observers have been tracking a chunk of space junk, waiting for it to strike the Moon. It should’ve hit the far side of the Moon, and hopefully, orbiters will have images of the impact site, though that might take a while.
The origins of the junk are in dispute. Some say it’s a spent booster from a Chinese rocket. Others say it’s from a SpaceX rocket. So far, nobody is claiming it.
New research shows that Mars has faced a constant rain of meteors during the last 600 million years. This finding contradicts previous research showing that the impact rate has varied, with prominent activity spikes. Why would anyone care how often meteors rained down on Mars, a planet that’s been dead for billions of years?
Because whatever Mars was subjected to, Earth was also likely subjected to.
This diagram shows the orbits of 2,200 potentially hazardous objects as calculated by JPL’s Center for Near Earth Object Studies (CNEOS). Highlighted is the orbit of the double asteroid Didymos, the target of NASA’s Double Asteroid Redirect Test (DART) mission. Credit: NASA/JPL-Caltech
An asteroid striking Earth is a genuine possibility. There are tens of thousands of asteroids classified as Near-Earth Asteroids (NEAs), and we’re finding around 3,000 more each year. The number of new detections will see an uptick in the next few years as better survey telescopes come online.
Now NASA has developed a new system to classify all those asteroids and better evaluate impact probabilities.
An artist's conception of an asteroid collision, in the belt between Mars and Jupiter. Credit: NASA/JPL-Caltech
This is our Great Question: How did life begin on Earth? Anyone who says they have the answer is telling tall tales. We just don’t know yet.
While a definitive answer may be a long way off—or may never be found—there are some clever ways to nibble at the edges of that Great Question. A group of researchers at Kobe University in Japan are taking their own bites out of that compelling question with a question of their own: Did the heat from asteroid impacts help life get started?
A three-dimensional cross-section of the hydrothermal system in the Chicxulub impact crater and its seafloor vents. The system has the potential for harboring microbial life. Illustration by Victor O. Leshyk for the Lunar and Planetary Institute.
How did life arise on Earth? How did it survive the Hadean eon, a time when repeated massive impacts excavated craters thousands of kilometres in diameter into the Earth’s surface? Those impacts turned the Earth into a hellish place, where the oceans turned to steam, and the atmosphere was filled with rock vapour. How could any living thing have survived?
Ironically, those same devastating impacts may have created a vast subterranean haven for Earth’s early life. Down amongst all those chambers and pathways, pumped full of mineral-rich water, primitive life found the shelter and the energy needed to keep life on Earth going. And the evidence comes from the most well-known extinction event on Earth: the Chicxulub impact event.
Mining asteroids might be necessary for humanity to expand into the Solar System. But what effect would asteroid mining have on the world's economy? Credit: ESA.
Plate tectonics have played a vital role in the geological evolution of our planet. In addition, many scientists believe that Earth’s geologically activity may have played an important role in the evolution of life – and could even be essential for a planet’s habitability. For this reason, scientists have long sought to determine how and when Earth’s surface changed from molten, viscous rock to a solid crust that is constantly resurfacing.
Some of the microtektites found by Mike Meyer inside fossilized clams in Florida. Image Credit: Photo by Meyer et al in Meteoritics and Planetary Science.
When an extraterrestrial object slams into the Earth, it sends molten rock high into the atmosphere. That debris cools and re-crystallizes and falls back down to Earth. Tiny glass beads that form in this process are called microtektites, and researchers in Florida have found microtektites inside fossilized clams.
The impact site of the LADEE spacecraft is clear to see. Actually not really. One must compare to LROC images of the same site photographed before and after the impact to locate it. Click on the image to view the animated gif holding the pair of images. (Photo Credits: NASA/GSFC/LROC)
Ever wonder what your refrigerator’s impacting at the speed of a tank artillery shell would do to the Moon? The Lunar Reconnaissance Orbiter’s (LRO) primary camera has provided an image of just such an event when it located the impact site of another NASA spacecraft, the Lunar Atmosphere and Dust Environment Explorer (LADEE). The fridge-sized LADEE spacecraft completed its final Lunar orbit on April 18, 2014, and then crashed into the far side of the Moon. LADEE ground controllers were pretty certain where it crashed but no orbiter had found it until now. With billions of craters across the lunar surface, finding a fresh crater is a daunting task, but a new method of searching for fresh craters is what found LADEE.
The primary purpose of the LADEE mission was to search for lunar dust in the exceedingly thin atmosphere of the Moon. NASA Apollo astronauts had taken notes and drawings of incredible spires and rays of apparent dust above the horizon of the Moon as they were in orbit. To this day it remains a mystery although LADEE researchers are still working their data to find out more.
The LRO spacecraft has been in lunar orbit since 2007. With the LROC Narrow Angle Camera, LRO has the ability to resolve objects less than 2 feet across, and it was likely just a matter of finding time to snap and to search photos for a tiny impact crater.
However, the LROC team recently developed a new algorithm in software to search for fresh craters. Having a good idea where to begin the search, they decided to search for LADEE and quickly found it. The LROC team said the impact site is “about half a mile (780 meters) from the Sundman V crater rim with an altitude of about 8,497 feet (2,590 meters) and was only about two tenths of a mile (300 meters) north of the location mission controllers predicted based on tracking data.” Sundman Crater is about 200 km (125 miles) from a larger crater named Einstein.
A Google Earth map display of the Moon shows the area of the western limb and the offset of the LADEE impact site relative to the crater Einstein. The Moon’s limbs are zones rather than a distinct line because of its libration. (Photo Credit: Google, Illus. T. Reyes)
The LADEE impact site is within 300 meters of the location estimated by the LADEE team. The ground control team at Ames Research Center knew the location very well within just hours after the time of the planned impact. They had to know LADEE’s location in orbit with split-second accuracy and also know very accurately the altitude of the terrain LADEE was skimming over. LADEE was traveling at 1699 meters per second (3,800 mph, 5,574 feet/sec) upon impact.
But still, finding something as small as this crater can be difficult.
Looking at these images, the scale of lunar morphology is very deceiving. Craters that are 10 meters in diameter can be mistaken for 100 meter or even 1000 meters. The first image and third images (below) in this article are showing only a small portion of the external slope of the eastern rim of Sundman V, the satellite crater to the southeast of crater Sundman. Sundman V is 19,000 meters in diameter (19 km, 11.8 miles) whereas the first image is only 223 meters across.
The following image, which is the ratioing of “before” and “after” impact images by LROC, clearly reveals the impact scar from LADEE. LADEE’s crater is only approximately 10 feet in diameter (3 m) with the ejecta fanning out 200 meters to the west by northwest. LADEE was traveling westward across the face of the Moon that we see from Earth, reached the western limb and finally encountered Sundman.
A high resolution LROC image of the LADEE impact site on the eastern rim of Sundman V crater. The image was created by ratioing two images, one taken before the impact and another afterwards. The bright area highlights what has changed between the time of the two images, specifically the impact point and the ejecta. Full resolution of the image (click) is 1 pixel per meter [1000 m on a side]. (Credit: NASA/Goddard/Arizona State University)In the third image of this article (above), only a 1000 meter square view of the outer slope of Sundman V’s eastern rim is seen. Rather than take the difference between the two images, which is essentially what your eye-brain does with an image pair, LROC engineers take the ratio which effectively raises the contrast dramatically. Sundman V crater is on the far side of the Moon but very near the limb. At times, due to lunar libration, this site can be seen from the Earth. In the Lunar Orbiter image, below, Sundman and satellites J & V are marked. The red circle in the image below is the area in which LROC’s high resolution images reside. Furthermore, the famous Arizona meteor crater east of Flagstaff would also easily fit inside the circle.
This Lunar Orbiter image shows the Sundman craters. The high resolution LROC images of the LADEE impact site easily fit within the red circle (2 km dia.) on “Sundman V” eastern rim. (Photo Credit: NASA, Illus. T.Reyes)
The discovery so close to the predicted impact site confirmed how accurately the LADEE team could model the chaotic orbits around the Moon – at least during short intervals of time. Gravitationally, the Moon is truly like Swiss cheese. The effects of upwelling magma during its creation, the effects of the Earth’s tidal forces, and all the billions of asteroid impacts created a very chaotic gravitational field. Where the lunar surface is higher or more dense, gravity is stronger and vice-versa. LADEE struggled to maintain an orbit that would not run into the Moon. Without a constant vigil by Ames engineers, LADEE’s orbit would be shifted and rotated relative to the Moon’s surface until it eventually would intersect the Lunar surface – run into the Moon. Eventually, this had to happen as LADEE ran out of propulsion fuel.
The blink comparator used by Clyde Tombaugh at Lowell Observatory to discover Pluto in 1930. The basic approach has since been translated into computer software capable of searching many times faster than a human. (Photo Credit: MWT Associates/Melitatrips)
The method used by the LROC team in its basic approach is by no means new. Clyde Tombaugh used a blink comparator to search for Planet X for several months and many frame pairs of the night sky. The comparator would essentially show one image and then a second of the same view taken a few nights apart to Clyde’s eye. Tombaugh’s eye and brain could process the two images and identify slight shifts of an object from one frame to the other. Stars are essentially fixed, don’t move but objects in our solar system do move in the night sky over hours or days. In the same way, the new software employed by LROC engineers takes two images and compares them mathematically. A human is replaced by a computer and software to weed out the slightest changes between a pair of images; images of the same area but spaced in time. Finding changes on the surface of a body such as the Moon or Mars is made especially difficult because of the slightest changes in lighting and location of the observer (the spacecraft). The new LROC software marks a new step forward in sophistication and thus has returned LADEE back to us.
The following Lunar Orbiter image from the 1960s is high contrast and reveals surface relief in much more detail. Einstein crater is clearly seen, as is Sundman with J and V satellite craters on its rim.
A NASA Lunar Orbiter image of the LADEE impact site. Einstein is actually an old low profile crater 198 km in diameter with 51 km “Einstein A” at its center. Sundman is also a low profile crater, 40 km diameter, with satellite craters J (10 km dia., southwest), V (19 km dia., southeast). (Photo Credit: NASA)
Five orbiters from India, the European Union and the United States will nestle behind the Mars as comet Siding Springs passes at a speed of 200,000 km/hr (125,000 mph). At right, Comet Shoemaker-Levy 9 impacts on Jupiter, the Chelyabinsk Asteroid over Russia. (Credits: NASA,ESA, ISRO)
It was 20 years ago this past July when images of Jupiter being pummeled by a comet caught the world’s attention. Comet Shoemaker-Levy 9 had flown too close to Jupiter. It was captured by the giant planet’s gravity and torn into a string of beads. One by one the comet fragments impacted Jupiter — leaving blemishes on its atmosphere, each several times larger than Earth in size.
Until that event, no one had seen a comet impact a planet. Now, Mars will see a very close passage of the comet Siding Spring on October 19th. When the comet was first discovered, astronomers quickly realized that it was heading straight at Mars. In fact, it appeared it was going to be a bulls-eye hit — except for the margin of error in calculating a comet’s trajectory from 1 billion kilometers (620 million miles, 7 AU) away.
It took several months of analysis for a cataclysmic impact on Mars to be ruled out. So now today, Mars faces just a cosmic close shave. But this comet packs enough energy that an impact would have globally altered Mars’ surface and atmosphere.
So what should we Earthlings gather from this and other events like it? Are we next? Why or why not should we be prepared for impacts from these mile wide objects?
For one, ask any dinosaur and you will have your answer.
An illustration of the Siding Spring comet in comparison to the Comet 67P atop Los Angeles. The original image was the focus of Bob King’s article – “What Comets, Parking Lots and Charcoal Have in Common“. (Credit: ESA, anosmicovni)
One can say that Mars was spared as were the five orbiting spacecraft from India (Mars Orbiter Mission), the European Union (Mars Express) and the United States (MOD, MRO, MAVEN). We have Scottish-Australian astronomer Robert McNaught to thank for discovering the comet on January 3, 2013, using the half meter (20 inch) Uppsala Southern Schmidt Telescope at Siding Spring, Australia.
Initially the margin of error in the trajectory was large, but a series of observations gradually reduced the error. By late summer 2014, Mars was in the clear and astronomers could confidently say the comet would pass close but not impact. Furthermore, as observations accumulated — including estimates of the outpouring of gases and dust — comet Siding Spring shrunk in size, i.e. the estimates of potentially tens of kilometers were down to now 700 meters (4/10th of a mile) in diameter. Estimates of the gas and dust production are low and the size of the tail and coma — the spherical gas cloud surrounding the solid body — are small and only the outer edge of both will interact with Mars’ atmosphere.
The mass, velocity and kinetic energy of celestial bodies can be deceiving. It is useful to compare the Siding Spring comet to common or man-made objects.
Yet, this is a close call for Mars. We could not rule out a collision for over six months. While this comet is small, it is moving relative to Mars at a speed of 200,000 kilometers/hour (125,000 mph, 56 km/sec). This small body packs a wallop. From high school science or intro college Physics, many of us know that the kinetic energy of an object increases by the square of the velocity. Double the velocity and the energy of the object goes up by 4, increase by 3 – energy increases by 9.
So the close shave for Mars is yet another wake up call for the “intelligent” space faring beings of the planet Earth. A wake up call because the close passage of a comet could have just as easily involved Earth. Astronomers would have warned the world of a comet heading straight for us, one that could wipe out 70% of all life as happened 65 million years ago to the dinosaurs. Replace dinosaur with humans and you have the full picture.
Time would have been of the essence. The space faring nations of the world — those of the EU, and Russia, the USA, Japan and others — would have gathered and attempted to conceive some spacecrafts with likely nuclear weapons that could be built and launched within a few months. Probably several vehicles with weapons would be launched at once, leaving Earth as soon as possible. Intercepting a comet or asteroid further out would give the impulse from the explosions more time to push the incoming body away from the Earth.
There is no way that humanity could sit on their collective hands and wait for astronomers to observe and measure for months until they could claim that it would just be a close call for Earth. We could imagine the panic it would cause. Recall the scenes from Carl Sagan’s movie Contact with people of every persuasion expressing at 120 decibels their hopes and fears. Even a small comet or asteroid, only a half kilometer – a third of a mile in diameter would be a cataclysmic event for Mars or Earth.
But yet, in the time that has since transpired from discovery of the comet Siding Spring (1/3/2013), the Chelyabinsk asteroid (~20 m/65 ft) exploded in an air burst that injured 1500 people in Russia. The telescope that discovered Comet Siding Spring was decommissioned in late 2013 and the Southern Near-Earth Object Survey was shutdown. This has left the southern skies without a dedicated telescope for finding near-Earth asteroids. And proposals such as the Sentinel project by the B612 Foundation remain underfunded.
We know of the dangers from small celestial bodies such as comets or asteroids. Government organizations in the United States and groups at the United Nations are discussing plans. There is plenty of time to find and protect the Earth but not necessarily time to waste.
