Astronauts aboard the International Space Station are set to welcome a most unusual guest, as "the Blob" blasts off into orbit on Tuesday.

An alien on its own planet, the Blob is an unclassifiable organism—neither fish nor fowl. Nor is it plant, animal or fungus.

As such, Physarum polycephalum—a type of slime mold—has long fascinated scientists and will now be part of a unique experiment carried out simultaneously by astronauts hundreds of kilometers above the Earth and by hundreds of thousands of French school students.

The slime mold first appeared on Earth around 500 million years ago, and defies conventional biology because it is made up of one cell with multiple nuclei.

While most organisms grow and reproduce through the division and multiplication of cells, Physarum polycephalum does not.

Many Perseid-related news stories and social media posts state that the maximum rate is about 100 meteors per hour, which is a lot. So, folks get excited and go out on the peak night, braving mosquitos and other nightly hazards. But they are often disappointed; we routinely hear, "I went out and only saw a few meteors. Not even 20, much less 100!" And they would be right. The problem is that the 100 per hour is a theoretical number used by meteor scientists and does not convey what people are actually going to see.

In the 1980s, meteor researchers were searching for a way to compare the meteor shower rates observed by various individuals and groups across the globe. People were reporting the rates, but the differences in sky conditions, radiant altitude and observer eyesight made getting a comprehensive view of shower activity difficult.

So, the meteor researchers put their heads together and came up with the concept of a ZHR, or Zenithal Hourly Rate. The ZHR is what you get after you correct the observed rates for the sky conditions, the altitude of the radiant above the horizon and observer biases.