Serene Geminid meteor shower has a rather catastrophic origin

However, Geminids originate from an asteroid (3200 Phaethon), which does not generally form a tail. Because an asteroid is composed of rock and metal, it is less affected by the Sun's heat than comets. 

“What’s really weird is that we know that Phaethon is an asteroid, but as it flies by the Sun, it seems to have some kind of temperature-driven activity. Most asteroids don’t do that,” said Jamey Szalay, a research scholar at Princeton University. 

Therefore, it has been challenging to determine how this asteroid triggers the meteor shower. Scientists had previously only investigated Geminids using ground-based instruments. 

Using Parker's proximity to the Sun, astronomers got some information, notably regarding the dust grains ejected by this asteroid as the sun’s gravitational power attracts numerous comets and asteroids passing from its surrounding. 

According to a NASA blog post, the Parker Probe does not have any dust detection equipment that would allow it to collect more specific data on asteroids’ bulk, composition, speed, and direction.

“However, dust grains pelt the spacecraft along its path, and the high-speed impacts create unique electrical signals or plasma clouds. These impact clouds produce unique electrical signals that are picked up by several sensors on the probe’s FIELDS instrument, which measures electric and magnetic fields near the Sun,” explained the NASA post. 

The catastrophic origin

The scientists built a model using the data gathered by the probe and combined it with three different meteor shower creation scenarios.

“There are what’s called the ‘basic’ model of formation of a meteoroid stream, and the ‘violent’ creation model. It’s called ‘basic’ because it’s the most straightforward thing to model, but really these processes are both violent, just different degrees of violence,” said Wolf Cukier, from Princeton University, and lead author on the paper, in an official release. 

Furthermore, the new model findings were compared to previous models developed using Earth-based observations.

The results indicated that the models predicting a violent formation were mostly calibrated with the Parker data. This implies that the Geminind stream might result from a massive collision of its asteroid with another celestial body or a gaseous explosion. 

The study is published in The Planetary Science Journal.

Study abstract:

The Geminids meteoroid stream produces one of the most intense meteor showers at Earth. It is an unusual stream in that its parent body is understood to be an asteroid, (3200) Phaethon, unlike most streams, which are formed via ongoing cometary activity. Until recently, our primary understanding of this stream came from Earth-based measurements of the Geminids meteor shower. However, the Parker Solar Probe (PSP) spacecraft has transited near the core of the stream close to its perihelion and provides a new platform to better understand this unique stream. Here, we create a dynamical model of the Geminids meteoroid stream, calibrate its total density to Earth-based measurements, and compare this model to recent observations of the dust environment near the Sun by PSP. For the formation mechanisms considered, we find with the exception of very near perihelion the core of the meteoroid stream predominantly lies interior to the orbit of its parent body and we expect grains in the stream to be ≳10 μm in radius. Data–model comparisons of the location of the stream relative to Phaethon's orbit near perihelion are more consistent with a catastrophic formation scenario, with the core stream residing near or outside the orbit of its parent body consistent with PSP observations.