Though evidence to-date shows we are the first advanced species, at least in our cosmic neighborhood, that doesn't mean it can't happen elsewhere. It is absolutely likely, because according to one estimate there are as many as 700 million trillion terrestrial planets just in the observable universe.
The moon is just a big rock in Earth's orbit now but things could have gone a lot differently in the distant past. In fact, there may have been two early windows of habitability for Luna.

In a new paper, astrobiologists say conditions on the lunar surface were sufficient to support simple lifeforms shortly after the moon formed from a debris disk 4 billion years ago and again during a peak in lunar volcanic activity around 3.5 billion years ago. During both periods, planetary scientists think the moon was spewing out large quantities of superheated volatile gases, including water vapor, from its interior.

With the discovery of a dozen new tiny moons of Jupiter that planet now has upwards of 79 moons. Are all-natural satellites of a planet moons?  Not really, not unless they are similar to our Moon in objective physical properties.   Many of these moons are like Phobos and Deimos, the moons of Mars, in terms of their gross physical properties. These are bodies which are in fact captured asteroids or very asteroid like.  Some formed with Jupiter and orbit in the same direction that it rotates, prograde.  Some orbit against the direction of Jupiters orbit retrograde orbit.

The asteroid Oumuamua ("scout from the distant past" in Hawaiian) was discovered on October 19, 2017 by astronomers at thr Pan-STARRS1 survey when it came close to Earth's orbit, within the orbit of Mercury, about a month after its closest approach to the Sun It was called an asteroid - but it may be a comet.

Why the confusion? There are more data about its trajectory. Oumuamua was unlike any asteroid or comet observed before. It sped past the Sun, approaching from "above" the plabe of the planets on a highly inclined orbit, moving fast enough (70,800 miles per hour as of July 1, 2018) to escape the Sun's gravitational pull and eventually depart our Solar System.
A cosmic crash 8 billion to 10 billion years ago was a defining event in the early history of the Milky Way and reshaped the structure of our galaxy.

The Sausage Galaxy lost and the Milky Way won, fashioning both its inner bulge and its outer halo. The wreckage is all around us and the paths of the stars from the galactic merger earned them the moniker "the Gaia Sausage."
By using infrared wavelengths, the HAWK-I infrared imager mounted on ESO's Very Large Telescope (VLT) in Chile was able to capture this image of the star cluster RCW 38.

RCW 38 is over 5,00 light years away (look toward the constellation Vela) and is composed of several short-lived massive stars that will eventually supernovae, but also has some 8,000 other x-ray emitting objects.
Life may be common amongst the stars, but perhaps very far away. But new research published in Nature hints that it could be much closer than we expected. And it may be on a world of water and ice. 
It seems that in a posthumous gift to humanity, the celebrated Cassini spacecraft may have revealed that Enceladus, one of saturn's great moons, holds the building blocks of life.

Years ago I used to participate in machine learning competitions hosted by Kaggle. It was a lot of fun and a great learning experience. Eventually I lost interest in Kaggle competitions, but I continued to do Data Science as a hobby. My hobby evolved into what I now understand is "Dysonian SETI". And it has now brought me back to Kaggle.

There is a feature of Kaggle that I had not tried previously: kernels. A kernel is a script with markdown (e.g. a Jupyter notebook) hosted by Kaggle. I decided to post an analysis as a kernel:

Dysonian SETI With Machine Learning
Assuming that alien life has to be like life on Earth is the safest way to scientifically search for evidence of it.  A recent paper on the arXiv by a research team from Oxford is likely to cause headaches for SETI.  In short it shouldn't since the Oxford team has made a basic error in the midst of a masterful application of statistical analysis.  When searching for the truly unknown one must assume as little as possible.   In theoretical physics the hall mark of a good theory is one in which the most testable implications follow from the fewest assumptions and adjustable parameters.   Such is true of most areas of science.  So too must this be true of astrobiology and searches for intelligent life.

Every Branch of the service has ranks and uniforms which reflect their  history, mission, and culture. A potential space force would not be any different in this regard.  Consider the lineage it would have being mainly influenced by the US Air Force, the US Navy, and NASA.   Each has a rank structure of some kind.    It may be wise to establish a “space force” as a corps not within the Air Force... but within NASA, much as NOAA and NPHS have had for a long time.   Here is my take on how this could or should look.    If you question the need for a Space Force watch this 60 minutes video from 2015.