Over the last few weeks, Asteroid 2024 YR4 has become a staple in science news columns. This space rock has a fluctuating but small chance to hit our planet around 12 pm UTC on December 22, 2032. This chance will likely drop to zero in the coming weeks, but the possible size and current risk of the asteroid have crossed a few thresholds that kick into motion the gears of the global planetary defense system. We take a peek behind the curtains at how that response is shaping up.
Planetary protection is serious business and of all natural threats that exist, it’s one that we can predict and do something about. Since 2014, there have been two UN-endorsed working groups that deal with dangerous space rocks: the International Asteroid Warning Network (IAWN), chaired by NASA, and the Space Mission Planning Advisory Group (SMPAG), chaired by the European Space Agency (ESA).
Eyes on the asteroid
IAWN (pronounced “I warn”) is coordinating the network of telescopes taking observations of this dangerous rock. There are dozens of stakeholders in this group and anyone who can help is. The observations provide ways to refine 2024 YR4’s orbit, increasing the confidence in the impact risk prediction.
As of February 12, the chance it will impact our planet is 2.1 percent according to NASA’s Center for Near Earth Object Studies and 2 percent according to ESA’s Planetary Defence Office. The methods are independent of each other, and they might give slightly different values. The respective teams check each other’s results, and as long as there’s broad agreement, it is good news. The value is expected to go to zero with more observations but so far has varied wildly, but that is perfectly normal.
The impact odds will stabilize almost certainly in April, where the current observation window closes until 2028.
Dr Robin Andrews
“There are a couple of reasons why the impact probability is so variable,” asteroid-killing expert, science journalist and author Dr Robin George Andrews told IFLScience. “One is that the asteroid was first discovered on the 27th of December, just two days after its closest flyby of Earth on Christmas Day, which meant that it was receding from the planet at an incredible speed. So only a handful of observations have been able to be obtained.”
Dr Andrews explained that the number of observations has increased in the last several weeks, especially following the activation of IAWN but the object is fading fast, becoming invisible to many telescopes. It’s not just the number of observations that are important but also the timeframe; currently, a lot of observations are taking place but what we need is a longer timeframe looking at the object to work out the orbital line 2024 YR4 is taking in space.
“Every new observation that comes in changes the trajectory of that line. Sometimes the final destination of this asteroid looks like it gets a little closer to Earth and sometimes it looks like it gets a little further away, so there’s still a lot of uncertainty,” Andrews continued.
“The impact odds will stabilize almost certainly in April, where the current observation window closes until 2028.”
Getting the world on the same page
While IAWN is active, SMPAG (pronounced Same Page) is not sitting idly. SMPAG is the workgroup that would propose strategies to deal with this asteroid. It has not been fully activated yet, but there has been a preliminary meeting in Vienna last week and they are monitoring the situation very closely.
“There is a certain threshold from which asteroids are not just scary or spectacular anymore, where they really become a threat to the people on the ground,” Richard Moissl, the head of ESA’s Planetary Defence Office, told IFLScience. Asteroid 2024 YR4 is at that threshold.
SPMAG activation requires an asteroid larger than 50 meters (164 feet) and our little danger rock is between 40 and 90 meters ( 131 – 295 feet). Based on the estimated composition it’s closer to the smaller end and stony type of asteroid.
We’re not frightened. We’re not scared. This is not an insurmountable task. We don’t stop, we just try to get better every step of the way.
Richard Moissl
While not a city killer, the projected possible impact locations stretch from the Pacific Ocean off Central America, across equatorial South America, over the Atlantic, through central Africa, by a corner of the Arabian peninsula, and then all the way through to India. Millions of people live in the risk corridor and the role of SMPAG is to provide the UN with plans on how to deal with the threat. And it might involve one or multiple space missions.
The current risk corridor for 2024 YR4’s possible impact in 2032.
“An asteroid impact would cause so much just damage in terms of buildings of infrastructure and everything that if you look at the cost and loss of financial value implied. A space mission pales in comparison,” Moissl told IFLScience.
The last time Earth experienced something quite like it was the discovery of asteroid Apophis in 2004 and the early measurements suggested a potential impact in 2029 and 2036. There was no SMPAG at the time, but the working group has learned lessons from that time and practiced trial runs and is using these weeks to refine plans and workflow. It might be a dress rehearsal, but they want to be ready.
Deflecting the asteroid before it gets here
The asteroid will be assessed for as long as possible. Space telescope JWST, a collaboration between NASA, ESA, and the Canadian Space Agency, will observe it in March and hopefully again in May, which should help narrow the uncertainty in orbit and size dramatically. If by then, the risk has not dropped to zero, SMPAG will officially activate.
[2024 YR4] also crosses the Moon’s orbit in the critical time frame and that would be a spectacle to behold, an impact of a 50-meter-sized asteroid on the Moon.
Richard Moissl
The group will plan missions to deal with this threat, which will then be passed onto the UN General Assembly, and then it will be up to nations to make the decision. SMPAG activation would be a major ramp-up of activity to get experts working on how to deal with this threat. If it was clear that the object was over 50 meters, SMPAG would be already active, but since this is on the threshold, the group is doing everything it can to prep without going full steam right this minute. Listening to Moissl explaining it, we can likely rest easy even if the chance of impact increases.
“We’re not frightened. We’re not scared. This is not an insurmountable task,” Moissl told IFLScience. “We don’t stop, we just try to get better every step of the way.”
The mission(s) would be similar to NASA’s extremely successful DART mission which altered the orbit of Dimorphos, the small moon of asteroid Didymos, and may have even created the first human-caused meteor shower. But to be effective, we need to know as much as we possibly can about this space rock – the deflector might break the asteroid, too.
“There are many things you do to fight off asteroids, but you can’t fight an asteroid if you don’t know it’s coming. Hitting something that’s 40 meters versus 90 meters is quite a different kettle of space fish. You don’t want to break the asteroid into pieces unless you are sure the pieces are so small that they will burn up harmlessly in the atmosphere,” Dr Andrews explained. “So it’s a bit easier to do for 40 meters, definitely harder for 90 meters.”
Asteroid 2024 YR4 might hit the Moon
Worst case scenario, the asteroid impacts Earth. The most likely scenario is that the asteroid flies by without a care. But there is a small chance for a best-case scenario. The estimate has a large uncertainty but there could be up to 0.5 percent chance of 2024 YR4 hitting the Moon.
Moissl excitedly walked us through that scenario: “[2024 YR4] also crosses the Moon’s orbit in the critical time frame and that would be a spectacle to behold, an impact of a 50-meter-sized asteroid on the Moon. It would be visible from Earth and there would even be new lunar meteorites that would arrive on Earth (nothing dangerous), but there is no guarantee. Definitely, a new observable moon crater would be the outcome!”
Asteroid 2024 YR4 will likely not be a danger to humanity but will provide us with a chance to refine our skills. Our species faces many challenges and threats but it seems that when it comes to dangerous Near-Earth Objects, we take them seriously and move with confidence.
