Let's Talk Asteroid Apophis, Planetary Defense and Elon Musk

It's time to talk about Apophis again, I guess. Please calm down first.

The asteroid is about 1,100 feet (340 meters) wide, was discovered in 2004 and will make a reasonably close flyby of Earth on Friday, April 13, 2029. Apophis will not hit Earth during that flyby; more on that later. Nevertheless, it's wide and close and has a snappy name, and the internet loves its asteroids.

That's presumably how SpaceX CEO Elon Musk ended up retweeting Joe Rogan's podcaster post of an Express story (lacking any news relevance) about Apophis. "Great name!" Musk tweeted yesterday (Aug. 18). "Would not worry about this particular, but a big rock will hit Earth eventually & we currently have no defense."

infographic: Asteroid Apophis Close Earth Flyby of 2029 Explained

Great name! Would not worry about this particular, but a big rock will hit Earth eventually & we currently have no defense. https://t.co/XhY8uoNNaxAugust 18, 2019

Let's dissect all this a bit. Musk and Rogan made headlines in September when Musk appeared on the latter's podcast for a three-hour discussion of Tesla During that appearance, Musk infamously smoked marijuana and sipped whiskey, which prompted a NASA review of commercial space partnerships, according to The Washington Post.

It is unclear whether or not it is referring to the asteroid's actual name, Apophis, or the "God of Chaos" terminology inserted by Rogan cited.

Asteroid 99942 was first dubbed 2004 MNP based on a formula marking its discovery and was given a formal name Apophis the next year. According to the International Astronomical Union, which name Apophis commemorates the "Egyptian god of evil and destruction who lives in eternal darkness."

Musk is mostly correct in his assessment of Apophis itself. The rock is dubbed as a Potentially Hazardous Asteroid for its relatively large size and relatively close approaches, but it is a very long way from potentially hazardous to actually impacting. Asteroid experts are confident it will not hit Earth at that time: They've calculated a trajectory 7.4 miles (12 kilometers) wide that passes through our journey. Scientists also ruled out a 2036 impact.

Related: Huge Asteroid Flies Apophis By Earth on Friday the 13th in 2029

(Image credit: ESA / Herschel / PACS / MACH-11 / MEP / B.Altieri (ESAC) and C. Kiss (Konkoly Observatory))

Apophis is just one of thousands of asteroids that scientists have identified. That includes nearly 900 near Earth objects more than 0.6 miles (1 km) wide and nearly 9,000 of them more than 459 feet (150 m), the class into which Apophis falls. A host of instruments on the ground and in space continues to spot more and more of these objects and gather the data necessary for scientists to calculate the 'trajectories'.

That said, these scientists can not guarantee Apophis and Earth will never meet. Although they have a very good sense of the rock 's trajectory, the tug of earth' s gravity will be in its future. Potentially, many people today, humans may indeed need to worry about Apophis.

Other space rocks could also be a problem, but right now, NASA has not spotted any asteroids with worrying trajectories. "No known asteroid poses a significant risk of impact with Earth over the next 100 years," according to the NASA's Planetary Defense Coordination Office website.

If that status changes, it would be scary, it would be a new risk in the world, just a new knowledge of our risk; the asteroid would have been identified.

Related: Even If We Can Stop A Dangerous Asteroid, Being Human May Mean We Do not Succeed

And that 's the whole point of scientists' efforts to find and study asteroids in our neighborhood: If we learn about an approaching asteroid a day in advance, there' s nothing we can do, as Musk implies. That was the case, most recently, for the asteroid that exploded over Chelyabinsk, Russia, in 2013. On other short times, humans may be able to mitigate the worst damage, by evacuating people or perhaps using a nuclear explosion to break the Earth's atmosphere.

But let's say that someone spotted an asteroid 10 years before it was to slam into Earth. That's a long enough time that humans could realistically muster a response, depending on the particular constraints of the asteroid. Such a mission would have a greater impact on the future than it would have in its orbit in such a way that it would miss its appointment with Earth.

The planetary defense community is already working to develop an effective response to the intricacies of an individual asteroid threat through hypothetical exercises.

Related: A Fake Asteroid Headed to Earth Can Really Make You Think

And while humans have yet to launch any planetary defense missions, that will change soon. One of SpaceX's own Falcon 9 NASA's rockets is due to launch Double Asteroid Redirect Test, or DART. In October 2022, the spacecraft will crash into the smaller half of a binary asteroid, then measure the deflection the impact causes. The exercise will help planetary defense experts better calibrate any future missions to the size of the threatening asteroid.

It's also worth pointing out that Musk's statement was made in the context of a retweet of an Express headline and link. Now is probably a good time to remind you that you are not one of many media outlets notorious for overhyping asteroid flybys to draw clicks.

That said, the Express headline does indeed make a very good point about the 2029 flyby, intentionally or not. NASA and other experts are certainly prepaid for the asteroid's visit – because it's an incredible opportunity for scientists to understand asteroids that are all around us.

Scientists believe Apophis matches at least superficially about 80% of the potentially hazardous asteroids they've spotted around Earth, and the 2029 close approach will be within the reach of a host of instruments. Scientists want to know, for example, how much does the flyby stretches and distorts? Apophis and how does solar radiation warm up one side of the space rock affects its orbital path.

And yes, that information, ounce gathered, will feed into the continuing work of planetary defense experts who have been working on the problem of predicting and mitigating asteroid impacts.

Meghan Bartels at [email protected] or follow her @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.