Scientists: DART impact of Dimorphos changed its orbit and reshaped the asteroid

Dimorphos shape change
Click for original graphic.

According to a new study, the DART impact of Dimorphos in September 2022 not only shortened its orbit around the larger asteroid Didymos, it reshaped the asteroid itself, warping its widest point sideways from its equator.

You can read the paper here.

More important, the scientists found that the changes evolved over time.

Over the following weeks, the asteroid’s orbital period continued to shorten as Dimorphos lost more rocky material to space, finally settling at 11 hours, 22 minutes, and 3 seconds per orbit – 33 minutes and 15 seconds less time than before impact. This calculation is accurate to within 1 ½ seconds, Naidu said. Dimorphos now has a mean orbital distance from Didymos of about 3,780 feet (1,152 meters) – about 120 feet (37 meters) closer than before impact.

Similarly, the reshaping of the asteroid into its present shape took time. As the scientists noted in their conclusion, “it takes time for a binary system to settle after a kinetic impact event.”

Because of Dimorphus’s rubble pile nature, its shape and orbit should continue to evolve over the coming decades, as more of the ejecta from the impact slowly falls back onto its surface and the asteroid surface adjusts over time. This in turn should also effect the orbit, though by only very tiny amounts.

I continue to wonder if the entire solar orbit of this asteroid binary system was impacted at all by these changes. Any changes would likely be tiny, but it is important to know to see if such an impact can actually do such a thing. To find out will take several more years, as ground telescopes continue to track the asteroid.

In October 2024 the European probe Hera will launch on a mission to this asteroid binary, with its arrival expected in December 2026. At that time we will get a much better look at both asteroids and how the impact affected them.

High School students discover new orbital changes from asteroid impacted by DART

In observing Dimorphos, the small asteroid that the probe DART impacted in September 2022, researchers as well as students at a California high school have discovered unexpected orbital changes.

Recent observations have indicated the asteroid is tumbling since the impact. However:

Dimorphos also appeared to be continuously slowing down in its orbit for at least a month after the rocket impact, contrary to NASA’s predictions. California high school teacher Jonathan Swift and his students first detected these unexpected changes while observing Dimorphos with their school’s 2.3-foot (0.7 meter) telescope last fall. Several weeks after the DART impact, NASA announced that Dimorphos had slowed in its orbit around Didymos by about 33 minutes. However, when Swift and his students studied Dimorphos one month after the impact, the asteroid seemed to have slowed by an additional minute — suggesting it had been slowing continuously since the collision. “The number we got was slightly larger, a change of 34 minutes,” Swift told New Scientist. “That was inconsistent at an uncomfortable level.”

Swift presented his class’s findings at the American Astronomical Society conference in June. The DART team has since confirmed that Dimorphos did indeed continue slowing in its orbit up to a month after the impact — however, their calculations show an additional slowdown of 15 seconds, rather than a full minute. A month after the DART collision, the slowdown plateaued.

One explanation proposed for this slowdown points at the spray of rocks and boulders that surrounded Dimorphos after DART’s impact. When some of those boulders fell back onto the asteroid, they might have caused the orbital slowdown, and as the number of new impacts dropped, the slowdown stabilized.

Now that a full year has passed since the impact, it is possible to assess the full orbital changes to the asteroid. Thus, a new report is expected shortly.

Hubble image shows several dozen boulders flung from Dimorphos

Boulders drifting from Dimorphos
Click for original image.

Using the Hubble Space Telescope, astronomers have photographed several dozen boulders that were flung off of the asteroid Dimorphos following the impact by the space probe DART. The picture to the right, reduced and brightened to more clearly show those boulders, was taken on December 19, 2022, four months after DART’s impact.

These are among the faintest objects Hubble has ever photographed inside the Solar System. The ejected boulders range in size from 1 meter to 6.7 meters across, based on Hubble photometry. They are drifting away from the asteroid at around a kilometre per hour.

The blue streak is the dust tail that has streamed off of Dimorphos since the impact, pushed away from the sun by the solar wind.

Dimorphus is dry, based on data obtained before and after DART hit it

Data collected by the ground-based Very Large Telescope (VLT) in Chile before and after the impact by the DART probe in September 2022 has revealed that the rubble-pile asteroid Dimorphos is very dry, with little or no water.

[The astronomers] observed the Didymos–Dimorphos system on 11 occasions, from just before the impact to about a month afterwards. MUSE [one of VLT’s instruments] is able to split the light from the double-asteroid into a spectrum, or rainbow, of colors, to look for emission at specific wavelengths that corresponds to specific molecules. In particular, Opitom’s team searched the ejecta for water molecules and for oxygen that could have come from the break-up of water molecules by the impact. However, no evidence of water was detected. Dimorphos, at least, seems to be a dry asteroid.

You can read the paper here.

Some theories prior to DART’s impact suggested that there could be ice within some inner solar system asteroids. Finding none instead suggests that inner solar system asteroids are very distinct and different from the icy comets and asteroids either coming from or orbiting in the outer solar system.

Scientists publish their results from the impact of Dimorphos by DART

Seconds after impact
Seconds after impact. Click for movie, taken by amateur
astronomer Bruno Payet from the Réunion Island.

Scientists today published five papers outlining their results from the impact of Dimorphos by DART, summed up as follows:

  • Dimorphos’s density is about half that of Earth’s, illustrating its rubble pile nature.
  • The orbital period around the larger asteroid Didymos was changed by 33 minutes.
  • The ejection of material from Dimorphos during the impact had a greater effect on the asteroid’s momentum than the impact itself
  • The mass ejected was only 0.3 to 0.5% of Dimorphos’s mass, showing that the asteroid was not destroyed by the impact.
  • The impact turned Dimorphos into an active asteroid, with a tail like a comet.

The data not only tells us a great deal about this asteroid binary itself, it suggests that this impact method might be of use in defending the Earth from an asteroid impact. There are caveats however. First, the orbital change was not to the system’s solar orbit, the path that would matter should an asteroid threaten the Earth, but to Dimorphos’s orbit around its companion asteroid. We don’t yet know the effect on the solar orbit. Second, the impact did not destroy this small rubble pile asteroid, which means such an asteroid might still be a threat to the Earth even after impact. Third, in order for an impact to be the right choice for planetary defense, detailed information about the target asteroid has to be obtained. Without it such an impact mission might be a complete waste of time.

The irony to all this is that we knew all this before the mission. DART in the context of planetary defense taught us nothing, so NASA’s claim that this mission was to learn more about planetary defense was always utter bunkum. The mission’s real purpose was the study of asteroids, but selling it that way was hard. The sizzle of planetary defense however was a better lobbying technique, and it worked, even if it was dishonest.

That the press was also fooled by it, and continues to be fooled by it, is a subject for a different essay.

More results from DART impact of Dimorphos

Didymos and Dimorphos as seen from Earth
Click for movie.

At a science conference this week scientists provided an update on the changes that occurred to the asteroid Dimorphos after it was impacted by the DART spacecraft in September, shortening its orbit around the larger asteroid Didymos by 33 minutes.

The image to the right is a screen capture from a short movie made from 30 images taken by the Magdalena Ridge Observatory in New Mexico, and part of a new image release of the asteroid pair.

It shows the motion of the Didymos system across the sky over the course of roughly 80 minutes, and features a long, linear tail stretching to the right from the asteroid system to the edge of the frame. The animation is roughly 32,000 kilometers across the field of view at the distance of Didymos.

According to the scientists, the impact displaced more than two million pounds of material from Dimorphos.

Observations before and after impact, reveal that Dimorphos and its larger parent asteroid, Didymos, have similar makeup and are composed of the same material – material that has been linked to ordinary chondrites, similar to the most common type of meteorite to impact the Earth. These measurements also took advantage of the ejecta from Dimorphos, which dominated the reflected light from the system in the days after impact. Even now, telescope images of the Didymos system show how solar radiation pressure has stretched the ejecta stream into a comet-like tail tens of thousands of miles in length.

Putting those pieces together, and assuming that Didymos and Dimorphos have the same densities, the team calculates that the momentum transferred when DART hit Dimorphos was roughly 3.6 times greater than if the asteroid had simply absorbed the spacecraft and produced no ejecta at all – indicating the ejecta contributed to moving the asteroid more than the spacecraft did.

This information is teaching us a great deal about these two particular asteroids, which could be used if for some reason their totally safe orbit got changed and they were going to impact Earth. However, NASA’s repeated effort to make believe this info would be useful for deflecting other asteroids is somewhat absurd. It is helpful, but each asteroid is unique. The data from DART is mostly helping astronomers get a better understanding of the geology of these specific asteroids, which will widen their understanding of asteroids in general. Planetary defense is really a very minor aspect of this work.

Hubble spots double tail of debris from DART impact of Dimorphus

Dimorphus double tail
Click for original image.

A series of images taken by the Hubble Space Telescope of the ejecta released when DART crashed into the small 525-foot-wide asteroid Dimorphus has found that debris forming a double tail trailing away from the Sun.

The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 11, 2022 by Hubble, and shows those two tails as close parallel debris trails.

Repeated observations from Hubble over the last several weeks have allowed scientists to present a more complete picture of how the system’s debris cloud has evolved over time. The observations show that the ejected material, or “ejecta,” has expanded and faded in brightness as time went on after impact, largely as expected. The twin tail is an unexpected development, although similar behavior is commonly seen in comets and active asteroids. The Hubble observations provide the best-quality image of the double-tail to date.

Following impact, Hubble made 18 observations of the system. Imagery indicates the second tail formed between 2-8 October 2022.

Though observations by telescope will continue for the years to follow, the real punchline to this event will be when the European probe Hera rendezvouses with the Didymous-Dimorphus pair in 2026 to perform several years of very close observations.

DART’s impact shortened Dimorphus’s orbit around Didymos by 32 minutes

LICIACube Explorer image of DART impact
LICIACube Explorer image just after the DART
impact. Dimorphus is the blob near the top.

After two weeks of analyzing the orbit of Dimorphus around its parent asteroid Didymos, astronomers have determined that the impact of DART on Dimorphus shortened its orbit by 32 minutes.

Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.

Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.

It also appears the ejecta from the impact — much greater than expected — helped propel Dimorphus, a result that I think was also not expected.

Researchers are now shifting to studying the debris and asteroid itself, to better understand what happened as well as the nature of Dimorphus itself. This will also include a European probe dubbed Hera that will launch in 2024 an dvisit both asteroids in 2026.

Two days after DART’s impact of Dimorphus, ejected dust extends like a comet tail out more than 6,000 miles

Dust tail from Dimorphus two days after DART impact
Click for full image.

Using a telescope in Chile, astronomers photographed the ejecta two days after the impact of DART into the 525-foot-wide asteroid Dimorphus, and detected a tail of dust extending out more than 6,000 miles.

The picture to the right, cropped and reduced to post here, shows that tail.

In this new image, the dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, not unlike the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view. … At Didymos’s distance from Earth at the time of the observation, that would equate to at least 10,000 kilometers (6000 miles) from the point of impact.

Didymos is the larger parent asteroid that Dimorphus orbits.

It is still too soon to get the numbers on how Dimorphus’s path in space was changed by that impact. In fact, we still really don’t have a clear idea what is left of Dimophus itself. The ejecta cloud needs to clear somewhat to see what’s hidden inside it.

Hubble & Webb make first coordinated observations, tracking DART impact of Dimorphus

Webb and Hubble together look at DART impact of Dimorphus
Click for full image.

For the first time scientists have used both the Hubble Space Telescope and the James Webb Space Telescope to observe the same astronomical event, in this case the impact of the DART spacecraft on the asteroid Dimorphus on September 26, 2022.

The two images to the right show the asteroid several hours after impact. Both telescopes also captured images before the impact as well. From the press release:

Observations from Webb and Hubble together will allow scientists to gain knowledge about the nature of the surface of Dimorphos, how much material was ejected by the collision, and how fast it was ejected. Additionally, Webb and Hubble captured the impact in different wavelengths of light – Webb in infrared and Hubble in visible. Observing the impact across a wide array of wavelengths will reveal the distribution of particle sizes in the expanding dust cloud, helping to determine whether it threw off lots of big chunks or mostly fine dust. Combining this information, along with ground-based telescope observations, will help scientists to understand how effectively a kinetic impact can modify an asteroid’s orbit.

When Webb was first conceived in the late 1990s, it was exactly for this reason, to combine Hubble’s optical vision with Webb’s infrared view. Though more than a decade late, it has finally happened.

It will be months before scientists begin to decipher the data produced by all the telescopes and spacecraft used to observe the DART impact. What we are seeing now are merely hints at what has been learned.

First ground-based telescope view of DART impact on Dimorphus

LICIACube Explorer image of DART impact

We now have the first ground-based images of the DART impact on the 525-foot-wide asteroid Dimorphus yesterday, captured by the Hawaiian telescope ATLAS.

You need to watch the video of the full sequence of images, available here, to get a true sense of the impact. The cloud of material quickly expands to about twice the asteroid’s size, then dissipates away, with the remaining asteroid now appearing larger (?). That larger size could be caused by a remaining cloud of material that still needs to settle back to the surface.

More images have been released by a Chinese telescope. Also, the first images from the Italian cubesat LICIACube Explorer, flying in parallel with DART, have been released. I have posted one to the right. The large blob near the center is the parent half-mile-wide asteroid, Didymos. Dimorphus is buried in the debris cloud above and slightly to the right.

Hat tip stringer Jay for the links to these images.

DART hits Dimorphus

Didymos and Dimorphus

Dimorphus

The surface of Dimorphus

The probe DART today successfully impacted the small 525-foot-wide asteroid Dimorphus. From the data produced engineers will calculate how much that impact changed Dimorphus’ orbit around it parent asteroid, half-mile-wide Didymos.

The three images to the right give a sense of the approach and impact.

The first, at 2 minutes and 30 seconds from impact, shows Didymos in the left bottom corner. You can actually see individual boulders on its surface. At this distance and resolution is is unclear whether it is a rubble pile or a more solid body. Dimorphus is no longer a mere dot, but no surface features can yet be discerned.

The second image, only seventeen seconds before DART crashed into Dimorphus, shows us the entire asteroid. Though it appears to be a pile of rocks, it also appears less of a rubble pile than both Ryugu and Bennu, visited by probes in 2019 and 2020. Those rubble-piles had almost no smooth surface areas. Dimorphus however at this distance and resolution does appear to have a lot of areas where the surface is relatively smooth, suggesting its structure is more solid than a rubble pile.

At only 525 feet across, some of those bigger boulders are about 50 to 60 feet in diameter.

The white dot in the center of Dimorphus marks the rocks seen in the third image, taken about five seconds before impact. At this resolution so close to the surface, it appears the smooth areas are actually made up of many tiny pebbles and dust.

The biggest rock in the center of the picture is probably between ten to twenty feet in diameter.

The primary data from this mission will not be available for a few weeks. Scientists have to observe both asteroids to see how much, if at all, Dimorphus’s orbit was shifted by the impact. Also, the images from the Italian cubesat, LICIACube Explorer, which was flying parallel to DART and taking pictures of the impact, plume, and back side of Dimorphus, won’t be available until later this week. Those images should give us a measure of the spacecraft’s effect on the asteroid. They will also reveal a lot more about the asteroid’s geology.

Watch DART smash into asteroid today

At 7:14 pm (Eastern) the NASA’s Double Asteroid Redirection Test (DART) spacecraft will crash into the small and harmless asteroid Dimorphus to see if such an impact could be used in the future to change the path of another asteroid aimed at Earth.

Dimorphus is 525 feet in diameter, and is a small moon of the larger half-mile-wide asteroid Didymos. Both are presently about 7 million miles away from Earth.

I have embedded the live streams below, one from a DART camera, dubbed DRACO, that will view the asteroid as the spacecraft approaches, and the other from NASA’s official live stream. From the DRACO live stream webpage:
» Read more

Watching DART impact asteroid on September 26, 2022

A NASA planetary probe, dubbed DART, is on course for a planned impact of the asteroid Dimorphos this coming Monday, September 26, 2022, at 4:14 PM (Pacific).

DART was launched from Vandenberg Space Force Base, CA on November 23, 2021 PST (November 24 EST) headed to the asteroid Didymos and its tiny moon Dimorphos 7 million miles away. The plan is for DART to ram itself into Dimorphos while scientists on Earth measure whether its orbit around Didymos changes.

Dimorphos is about 525 feet in diameter, while Didymos is much larger, about a half mile in width. The goal is to see if this method can be used in the future to adjust an asteroid’s orbit enough to shift it away from hitting the Earth.

The impact will be observed by a camera on DART, as well as an Italian cubesat dubbed LICIACube.

NASA TV will be live streaming the event, and I will embed that live stream here when it goes live. Once DART gets close, its camera will record the asteroid’s approach through impact.

September 13, 2022 Quick space links

Courtesy of stringer Jay.

August 24, 2022 Quick space links

Links courtesy of BtB’s stringer Jay.

SpaceX successfully launches NASA asteroid mission

Last night SpaceX’s Falcon 9 rocket successfully launched NASA’s DART asteroid mission.

The first stage landed successfully, completing its third flight. This was SpaceX’s 26th launch in 2021, setting a new record for the company and in fact for any private company ever.

DART’s mission is to test one method for changing an asteroid’s orbit.

After launch tonight, DART will take aim on an asteroid called Dimorphos. The spacecraft will strike Dimorphos at nearly 15,000 mph (about 6.6 kilometers per second).

The primary science goal of the mission is to measure how the high-speed collision next September, which will destroy the DART spacecraft, disrupts the orbit of Dimorphos around nearby Didymos. The data could help plan a future mission to deflect an asteroid on a course to hit Earth.

Dimorphos and its larger companion Didymos pose no near-term threat to Earth, but the asteroids will be close enough to our planet next year for astronomers to observe DART’s impact using ground-based telescopes. The asteroids orbit the sun in an elongated path that occasionally bring them into Earth’s neighborhood. That makes them potentially hazardous asteroids, although scientists say there is no near-term threat from the pair.

No space mission has ever explored Didymos and Dimorphos, but scientists who have observed them through telescopes say the asteroids are about a half-mile (780 meters) and 525 feet (160 meters) in diameter, respectively.

An Italian cubesat is also on board, and will separate from DART about ten days before impact so that it can observe the impact with two camera.

The leaders in 2021 launch race:

43 China
26 SpaceX
18 Russia
5 Europe (Arianespace)

China now leads the U.S. 43 to 41 in the national rankings. For the U.S. SpaceX’s launch last night topped the U.S. total from last year, which was this country’s highest launch total since the 1960s.

SpaceX gets NASA launch contract

Capitalism in space: One week after dropping its protest for losing the bidding competition for the Lucy asteroid mission, SpaceX has been awarded by NASA the launch contract for its Double Asteroid Redirection Test (DART) mission, set for launch in June 2021.

The $61 million launch price is significantly lower than past NASA contracts for Falcon 9 launches. NASA awarded SpaceX a contract for the Sentinel-6A satellite in October 2017 for a November 2020 launch on a Falcon 9 from Vandenberg at a total cost of $97 million. The Surface Water and Ocean Topography (SWOT) satellite will launch on a Falcon 9 in April 2021 under a contract awarded in November 2016 at a value of $112 million.

This low cost technology test mission, costing a total of $9 million, was initially going to be launch as a secondary payload. That NASA is now going to pay SpaceX for a full launch is most intriguing. It seems to me that there might be a bit of quid pro quo here. NASA wanted that protest dropped, and offered this launch to convince SpaceX to do that, as long as the launch cost was kept low. $60 million is really SpaceX’s standard price for Falcon 9 launch, using new boosters, but for NASA that is the least they’ve paid. How much more this is than what NASA would have paid to launch DART as a secondary payload is the real question.