I’m aware that the title sounds hokey, but I would like to make two simple points so stick with me.
The Size of Our Universe
Our Earth is part of a solar system. It’s called a solar system because, at its center, is a sun (sol is Latin for sun). Our solar system is part of the Milky Way galaxy. Specifically, it is one of roughly 400 billion solar systems in the Milky Way (source: NASA SpacePlace). Our Universe, contains 100-400 billion galaxies like the Milky Way. Here’s a graphic to ponder while that information sinks in:
So, there are roughly 400 billion x 100 billion = 40 sextillion planets in the Universe.
“What the heck is a sextillion?”, you ask. That’s 40 thousand billion billion planets. (That’s right, the billion billion is not a typo.)
Just imagine the scale of that number! You might see that the Earth, no matter how special, is unfortunately not that special. It’s quite possible that there are other forms of life out there, and we/they just haven’t gotten in touch.
Alien Protein Discovered on Meteorite
As I type this sentence, the following is breaking news. In Feb 2020, scientists at Harvard University (and their industrial collaborators at PLEX Corp. and Bruker) reported the structure of an extraterrestrial protein called Hemolithin discovered on the surface of a meteorite . Below is the structure of the amino acid polymer:
Hemolithin contains building blocks (called amino acids) such as glycine and hydroxy-glycine that are also found on earth. It gets really strange when you see that this protein also incorporates lithium and iron (orange and green dots, respectively, in the bottom panel of the figure), which seem to be holding two chains of the protein together. Proteins existed before life on Earth could emerge (~3.8 billion years ago). That’s why bacteria, humans, plants, extremophiles, and everything in between shares the same set of ~20 amino acid building blocks. The type of protein chemistry comprising Hemolithin is unprecedented, and a strong indicator of extraterrestrial life.
Anticipating your questions, I’ve made 2 more salient points below:
(1) How can you tell Hemolithin is extraterrestrial if it was discovered on a meteorite found on Earth?
– Elements like carbon, hydrogen, nitrogen, and oxygen exist as isotopes. Isotopes are atoms of the same element with slightly different masses (because of more or less neutrons). These isotopes differ in their relative amounts based on where they come from in the Universe. For example, 98.9% of carbon on Earth has a mass of 12 units. But 1.1% of carbon has a mass of 13 units (because of an extra neutron). So, carbon-12 and carbon-13 are isotopes, but have different relative abundances. Using a highly sensitive instrument called a mass spectrometer, McGeoch, et al. analyzed relative isotope abundances of the hydrogen and nitrogen elements in Hemolithin. They found that these numbers didn’t match established records for Earth. For example, a rare hydrogen isotope (hydrogen-2) was enriched 27,500 parts per thousand. This kind of variation physically cannot occur on Earth, confirming extra-terrestrial origin.
(2) So…aliens exist for sure?
– Well, no. First, we need to be able to see alien life to confirm it. Discovering a single protein (or small part of it) doesn’t meet that criterion. Second, proteins are required for life (on Earth, at least), but life does not necessarily exist if we find proteins. It is equally likely that this protein is the beginning of life on a planet far far away. Life might already exist, or it will spark on Hemolithin’s planet after 10 billions years. It’s impossible to predict.
Here are some questions I would like answers to:
– Meteorites experience temperature extremities, UV rays, and other chemical catalysts. Could it be that the lithium and iron atoms were somehow “appended” to the structure of Hemolithin while it made it’s way to Earth on a meteorite?
– What are Hemolithin’s functions/capabilities? McGeogh, et al propose, based on chemical motifs containing iron found in the protein, that it might absorb photons and split water into hydroxyl (OH-) and hydrogen (H+) moieties. Much more information and testing is required.
I hope I have compelled you to (re)consider that alien life might exist in our Universe. Nobody knows for sure, but there’s a lot of smoke so there might be a fire? If you have more questions or comments, leave a comment!
 McGeoch, Dikler, and McGeogh. Hemolithin: a Meteoritic Protein containing Iron and Lithium. 2020. arXiv:2002.11688v1.
 NASA SpacePlace: https://spaceplace.nasa.gov/review/dr-marc-space/solar-systems-in-galaxy.html