Apparently the pattern on the Perserverance lander parachute is encoded in ASCII. How does ASCII work, and how does that encryption in color translate to text?
In: Mathematics
ASCII is basically just a mapping of characters (like ‘A’) to numbers (specifically numbers that are can be represented by 8 binary bits, which are the numbers between 0 and 255). For example, ‘A’ is represented with the number 65 (which when written in binary is 01000001).
The benefit of ASCII is that it lets you write text anywhere you have two things you can use to represent 0 and 1, like wires being on or off in a computer, or, say, alternating colors on a parachute pattern.
ASCII is a list of characters in a well known order. When encoding ascii to binary you first find its decimal position in the table, then convert that decimal number to binary. It is helpful because computers can only run programs with binary so by having a common standards it makes computers compatible with each other. [link](https://www.rapidtables.com/code/text/ascii-table.html)
The message is encoded in binary, but not in ASCII. NASA used the simplest possible way to encode letters as numbers (A=1, B=2, etc.) ASCII is also a way to encode letters (and other stuff) as numbers, but there A=65, B=66, etc. because there’s a bunch of other stuff before it in the sequence like punctuation and control characters.
So the actual message is 4 1 18 5 (DARE) 13 9 7 8 20 25 (MIGHTY) 20 8 9 14 7 19 (THINGS), but the numbers are in binary. There are lots of sources that will tell you how binary works, but all you need to understand this is to know that in a 4-digit binary number:
If the rightmost digit is 1, add 1
If the digit second to the right is 1, add 2
If the digit third to the right is 1, add 4
If the digit fourth to the right is 1, add 8
If the digit fifth to the right is 1, add 16
So the binary number 11001 is 16 + 8 + 1= 25 = Y
Instead of writing 0s and 1s, NASA instead colored some sections of the parachute red to indicate a 1.
The last step in decoding it was figuring out how to “read” the parachute. Someone eventually discovered (probably after trying a bunch of different things) that they should read in lines from the outside to the inside, moving clockwise, then break the digits up into groups of 10. There’s no particular reason to encode it this way other than the fact that NASA also wanted to encode the GPS coordinates of the JPL on the outermost part of the parachute and because just “Dare mighty things” would only take about 100 segments, while the whole parachute had many more (probably for good engineering reasons that weren’t going to be ignored for a little secret message).
Latest Answers