I’m revisiting a post from a few years ago that was inspired by a NASA press release in 2011. That press release was widely copied because it referenced attempts to identify the source of an asteroid that may have killed off the dinosaurs. What caught my eye in that press release was a reference to the age of asteroid families what made me wonder: how on Earth, or the Universe:-), did these astronomers determine the age of these asteroids? I did a little bit of reading and found the answer to be quite fascinating.
So just what is an asteroid family? You might think of the asteroid belt between Jupiter and Mars as an assortment of space junk floating randomly in space. There are millions of asteroids of which more than 100,000 have been measured and locations mapped by astronomers. But analysis of those asteroids has shown that there are groups of asteroids that are related to one another and are referred to as family members due to similar orbits, composition, dust covering etc… They are called families because it is believed they are related to a common ancestor. This common ancestor was an large asteroid in the past, the parent, that was hit by another object causing the parent to break into multiple pieces which become daughter asteroids. In some cases the parent is destroyed and is survived only by its children and in other cases the parent may survive with only pieces breaking off yielding a family with a surviving parent.
In the case of the family of asteroids in the press release above, over 1000 individual asteroids were identified as fragments of a deceased parent asteroid. Just how old is this asteroid family named the Baptistinas? There is simple, though technically challenging, way to infer the age of families like the Baptistinas. If orbital measurements such as direction and speed can be made for many members of the family then one can infer backward to when all the members of the family where once only found in the parent astroid. In the case of the Baptistina asteroid family this has been done and the family estimated to be about 80 million years old. This is just the age since the breakup, not the age of the material of the asteroids themselves. There are many theories about the origin of the first member of the asteroid belt most of which involve events that occurred on the scale of billions of years ago.
Another asteroid family, the Karin asteroid family, is much more interesting because more is known about it. More than 90 members of this family have been identified but more importantly 13 of those have had their orbits carefully mapped and using those maps scientists have run the orbital patterns backwards in time to find the time when all 13 pieces would have coalesced at one point in time. That calculation yielded an estimated age of the parental asteroid of 5.8 million years ago with only a 0.02 million year variance (error) in their measurements. This is the “youngest” appearing family known in the asteroid belt between Mars and Jupiter. Further evidence of the “youth” of this family is the high reflectivity of the daughter asteroids due to their lack of dust buildup owing to their recent break-up. They are also clustered much closer to one another in space than other much older asteroid families which have had much more time to disperse.
Given enough time the family members of any asteroid family will disperse to such an extent that they will intermingle with the descendants of other families and just look like a random jumble of asteroids.
Asteroid Families and the Young Earth Worldview
Asteroids families are remarkable evidence of the great age of the solar system. I find asteroids and other planetary evidence (Finding Mars on Earth: A conversation about Mars meteorites and A Young Mercury: apparent age redux) of the long history of our solar system to be one of the biggest challenges to the young earth creationist (YEC) worldview. For geological features on Earth that appear old,YECs appeal to a massive global event (Noah’s flood) in recent history to explain the fast layers of rock and billions of fossils contained in that rock. But in space or on other planets a global flood not an option as an explanation for features that appear to be the result of millions of years of development. Not that some YECs haven’t tried to expand the effects of a flood on Earth to the solar system (see my article: Walter Brown and the Origin of Asteroid and Impact Craters on Other Planets).
Asteroid families and rotating asteroids (see: As the asteroid tumbles: Asteroids and the Age of the Solar System) are so challenging to the idea of a youthful solar system because they depend on extrapolations with very simple assumptions. In the case of asteroid families, we can measure the speed at which pieces of a broken asteroid are drifting away for each other. We can take those rates of drift and calculate back. Those calculations lead us to age estimates of millions to 10s of millions of year these the best studies asteroid families.
If the solar system were young then YECs can respond to this evidence of its great age in one of three ways:
1) Deny that the asteroids are part of a family and suggest that the characteristics that suggest they are related to each other (orbits, composition, etc..) are just coincidences. Rather than having a common ancestor each asteroid was created individually and has no relationship with any other.
2) Accept that the asteroid families represent daughters of a parent breakup but insist that breakup occurred within the past 6000 years. For this to be true then the speeds that they are traveling away for each other must have changed greatly over time. Thus for them to have achieved the great distances (millions of miles!) between them we see today they would have had to be traveling very fast in the past but then slowed to their present speed. But what would cause this change in speed in the depths of outer space where there is virtually no friction? Supernatural intervention would seem to be the only option.
3) Accept that the asteroids are part of a family but employ the apparent age defense. Apparent age posits that God created the pieces of these large asteroids in their present orbitals to appear that they one were part of ancestral parent. There never was a real-time when they were together but the pieces have the appearance of looking as if they have the same parent. Henry Morris and other YEC types have tried to separate apparent age into two types. I have elaborated on apparent age in other posts (Apparent Age: Crater on Mars and A Young Mercury: Apparent Age Redux) but simply they try to make a distinction between “essential appearance of age” and “deceptive appearance of age”. Essential age is also couched in terms like “necessary” or “superficially” to give the idea that there isn’t a specific history embedded in an object but only the necessary appearance of age like a full-grown human who would appear to have grown from a baby. I have difficulty describing the differences between these types of apparent age because they make so little sense to me.
My best guess is that “essential” age for astronomical features like light coming from a star that is created old is fine but light coming from a star with information recording an explosion of that star that never happened is not OK and would be considered “deceptive” age. For our example of asteroid families, I would imagine that a set of asteroids with orbits and characteristics that attest to a past history as one unified object millions of years ago would have to be classified as deceptive. But if this is deceptive age then explanation #3 is out. That leaves only changing rates of motion over time probably due to changing laws of physics or just denying that families of asteroids even exist. Neither of these are simple or obvious rationales for ignoring this evidence of an ancient solar system.
This NASA article is another in a long line of observations and reports that Christians are confronted with everyday that directly or indirectly provide evidence of the great antiquity of the solar system and universe. Most of these evidences involve simple processes that are most easily interpreted within an old-age framework. YECs try to reinterpret this data to fit a young universe model but in doing so the must propose many ad-hoc hypotheses. Often when faced with no viable explanation they turn to the only tried-and-true defense which is to claim NASA has a bias and therefore the data itself is suspect. However, this requires one to buy into a massive conspiracy to distort data and its interpretation and that conspiracy must include a large number of Christians working for or with NASA on hundreds of projects.
Asteroid families are the not the final proof that the solar system is older than 6000 years but they certainly should give any young earth creationists a reason to reexamine their presuppositions and ask themselves if their young universe view is truly required by scripture or has become an extra-scriptural article of faith laid on scripture by man.