Robert Zubrin points out the problems with the radio SETI program.
The Mars Reconnaissance Orbiter has a 100-watt transmitter using a 2-meter dish and we use a 70-meter dish to receive data at 6 megabits per second at 100 million kilometers.
A ten-light year transmission would be one trillion times slower at 200 bits per year. If the power of the transmission was 100 megawatts then we could increase the data rate to 6 bits per second. If aliens were transmitting then they would need to target many possible worlds.
Nextbigfuture would note that optical imaging of exoplanets and receiving of radio transmissions would all be enhanced with telescopes and receivers at the gravitational lensing points. Power levels would be reduced for the radio receiving because the sun would be acting as a 800,000-kilometer focusing dish. It would also be less random in terms of targeting because exoplanets could be imaged at gigapixel levels.
Zubrin Proposes Microsail Craft to Spread Engineered Bacteria for DNA Interstellar Messaging
Zubrin proposes tiny microsails shaped like badminton birdies for passive stability. They have a thin layer of material to protect DNA in bacteria from ultraviolet. The ultraviolet is why naked panspermia will not work. Another deisng
They would be propelled at 30 kilometers per second. It would take 100,000 years to 10 light-years.
The design would hit an atmosphere and decelerate without heating.
The messages would most likely be propoganda to encourage aliens to be like the sending aliens.
There are close passes of less than one half of a light-year with other solar systems every 20 million years. There is an exchange of Oort comet cloud material during those events. There is also an interesting fact that mass extinctions also occur every 20 million years.
Our bacteria is in our Oort comet cloud.
There have been about 180 close passes since the appearance of life on Earth.
Looking for DNA Messages
SOURCES- Robert Zubrin
Written By Brian Wang, Nextbigfuture.com