It brings me tremendous joy to share some of my favorite micrometeorites from early on in my journey as a Star Hunter. When I finally cracked the code and could identify micrometeorites based on appearance, their beauty and variation struck me in a way I could never have imagined. Today, it is my pleasure to introduce you to yet another iconic micrometeorite, NMM 244.
It is a classic cryptocrystalline (CC) type, known as a “turtleback”, with a nickel-iron bead in the front. In this updated photo by Jan Braly Kihle and yours truly, the front-facing bead is in the center. Its only average feature is its size, as the stone measures approximately 0.3 mm.
During formation, as this little space gem screamed through the atmosphere at hyperspeed, the frictional heat melted the micrometeoroid completely. The dense metal differentiated and became a liquid metal core inside the molten rock. Immediately after, the continuous friction caused by molecules in the atmosphere decelerated the little speck of stardust.
As the particle slowed, inertia pushed the heavy metal core forward to the front, where it was held back by surface tension. At the same time, the deceleration caused a drop in temperature and the metal triggered re-crystallization in the main mass. Small olivine crystals began to form and increased in size gradually until the entire stone was solidified.
Then the micrometeoroid fell to the ground at terminal velocity.
Reading through the steps, it may seem like this process would have occurred over minutes. However, this iconic micrometeorite’s entire formation was over in the blink of an eye. Isn’t that incredible to think of?
Solving the mystery of each micrometeorite’s formation is one of my favorite aspects of this work. I hope you’ve enjoyed taking this cosmic journey with me and I look forward to connecting with you on Facebook, Instagram, and Twitter.