+3 votes
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asked in Estimation by (560 points)
edited by | 506 views

2 Answers

+1 vote
Assumptions:

We are talking of a small colony on Mars with say 1000 people to begin with. If we are talking half the planet then calculations need to be different.

Gmail is the only email communication channel available on Mars as we don't have established networks and competition. Basically NASA has set Gmail to be the standard for email communication.

On Mars:

Average number of emails exchanged within the community per day: 5 community announcements and 5 personal emails. On earth I don't send more than 5 personal emails every day. So total 10 emails per day.

Size of email: Pure text runs less than 10KB but let's assume that every email has some kind of picture attachment that is optimized. So size of single email could be 200KB.

Total number of bytes: 200KB * 10 * 1000 = 2,000,000,000 bytes for intra Mars communication.

Those 1000 people have on an average 5 family members back home that they interact with daily. Let's assume one communication in and one out. So average 2 emails per day.

1000 * 5 * 2 * 200KB = 10,000 * 200,000 = 2,000,000,000 bytes between Mars and Earth for family.

These 1000 people have on an average 20 friends that they interact with twice a week. So that makes it 4 messages per week / per person. So 1000 * 4 * 20 / 7 = 1200 messages to friends on earth per day.

1200 * 200KB = 120,000,000 bytes per day.

Let's add up = 2B Mars community  + 2B family + 120M friends.= 4.2 B bytes per day = 4.2 GB per day.

Please note: What they are looking for is GBPS. That is the measure of true bandwidth. My calculations go haywire when trying to convert to GBPS.

I am looking for a response to that.
answered by (13 points)
0 votes

I struggle with these bandwidth/cost of storage type questions but I will go ahead and take a shot because why not?

I am going to calculate bandwidth requirement with the following formula:

Gmail users in Mars * Average bandwidth allowed by Gmail (upload and download) per day

Gmail users in Mars:

Google just announced that it now has more than 1 billion active users on Gmail. That’s not super useful because it does not tell us a relative %. Well maybe we can say that the world has 8 Billion people and if 1 billion of them are active on Gmail, then Gmail has a 12.5% share of the world’s population.

Lets assume that the people who build a community on Mars will be millenials, Gen z folks and they will have a higher Gmail penetration – lets say closer to US’s penetration = 30%.

How many people will live on Mars? Mars is half the size of Earth but Earth is 70% covered with water. And Mars has no water. So, lets say that Mars can roughly accommodate all of earth’s population because people can live all over the place. But due to it being a newly inhabited planet, lets say we ultimately end up with 1/4th of the population = 8/4 = 2 Billion people

Out of this 30% will use Gmail (based on our earlier adoption assumption) = 0.6B = 600M

As per Gmail documentation each person is allowed
Download: 1250 MB
Upload: 500 MB

If Gmail plans for this size to be available to each user per day, then total size per user per day = 1750 MB per day = 1.75 GB per person per day

Total bandwidth required per day = 0.6 GB people * 1.75 GB storage

answered by (149 points)
+2
Thanks for the answer. Couple notes:

– I think it’s important to know for what year / decade we are estimating bandwidth of Gmail in Mars. If it’s 10 years after first commercial travel to Mars, the population will most likely not be in billions. Let’s assume it’s 10 years after the first trip. In that case, population will most likely be # of travels made to Mars x # of passengers per spacecraft. We can also state a couple assumptions here: no one is coming back to earth from Mars. Population is not changing (death rate = birth rate), etc.

– I wouldn’t look at Gmail documentation to determine bandwidth per person. You can estimate the actual bandwidth used per Gmail user by multiplying two numbers (average size of an email, # of emails sent / received per day).
0
Thank you!

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