Could Earth have sent life to Jupiter's moon Europa?

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Could Earth have sent life to Jupiter's moon Europa?
by David Appell, Phys.org

edited by Sadie Harley, reviewed by Robert Egan
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Could Earth have seeded Jupiter's moon Europa with bacterial life, where 
it could have taken hold in Europa's ocean and perhaps evolved into 
something more? That's the hypothesis of a new paper in the 
International Journal of Astrobiology by Zaza Osmanov of the Free 
University of Tbilisi in Georgia.

Osmanov calculates the chance that dust particles containing living 
bacteria were ejected from Earth's gravitational well and traveled to 
Jupiter's icy moon Europa, where they could have landed undestroyed and 
made their way through cracks in Europa's ice, beneath which lies a vast 
sea that scientists believe could harbor life.

The possibility of panspermia, bringing simple life to Earth from 
elsewhere in the universe, has been discussed for decades. Dust, 
meteoroids, asteroids and comets might all have contained life forms as 
they crashed into Earth.

The hypothesis is impossible to test experimentally, but in a paper 
published in the International Journal of Astronomy and Astrophysics, 
Osmanov, who is also affiliated with the E. Kharadze Georgian National 
Astrophysical Observatory, calls this the "reverse panspermia problem" 
and calculated that "in 5 billion years dust grains can travel in the 
interstellar medium at distances of the order of hundreds of parsecs."

Also, given the distribution of stars in the Milky Way, "particles 
emitted by every single planet will reach as many as 105 stellar 
systems." Moreover, Osmanov found that from a single planet, life can be 
transported to about a thousand star systems.

The red line is the trajectory of a dust grain traveling from Earth, at 
1 astronomical unit (AU), to the vicinity of Jupiter at 5 AU, using the 
parameters and assumptions utilized in the text. Credit: Used with 
permission of Zaza Osmanov.
How the Europa case works
Using techniques similar to those in his earlier paper, Osmanov 
considered Earth as an origin of dust grains, and Europa, with its 
unique ice and ocean features, as their end point. Osmanov breaks his 
analysis into three parts:

Could dust grains carrying life have escaped Earth's gravitational 
field, and in what abundance?
Could such dust grains have landed on Europa in a way that didn't 
destroy them, and in what numbers? And 3. If they landed, could such 
grains have permeated Europa's thick crust of ice and reached its liquid 
surface?
Dust particles about a micron (a millionth of a meter) in size can 
contain packed bacteria of about the same size. Moreover, for the 
bacteria to survive any journey, their temperature cannot exceed about 
300 Kelvin (about 27°C).

Dust grains are carried aloft by atmospheric turbulence; considering the 
energy imparted to one at 150 kilometers (93 miles) in altitude, as 
through a collision with cosmic dust, Osmanov's 2025 paper allowed him 
to calculate a maximum imparted velocity of the dust grain of 14 km/s at 
altitude, which exceeds Earth's escape velocity of 11.2 km/s.

More simple physics shows the particle would have a velocity of 8.4 km/s 
when far from Earth, about 10% faster than the International Space 
Station circles the planet. This would be happening for the entire 3.5 
billion years that simple life has existed on Earth.

 From Earth to Europa
After leaving Earth, three forces act on the dust particles: the 
pressure of radiation from the sun, the gravitational force of Jupiter 
(which dominates the sun's gravitational force after the grain has 
traveled about 97% of the sun-Jupiter distance), and the average drag 
force of the interplanetary medium in the solar system.

Osmanov solves the dust grain's equations of motion to find that its 
velocity at Jupiter is 20.1 km/s. The impact of the grain on Europa is 
at a maximum when it comes directly downward relative to the moon's 
surface. Using the dust grain's specific heat, he finds that only grains 
that come in at a very low angle—1 degree relative to the surface—will 
survive the impact, meaning only about three in a thousand bacteria 
packs survive the landing.

A flux of about one particle per square centimeter per second leaves 
Earth through a collision with cosmic dust in the atmosphere, or about 5 
x 1018 total particles per second, ejected equally in all directions. 
Using geometry to find the fraction of dust particles that enter 
Jupiter's gravitational zone, Osmanov finds that about 300 million such 
particles from Earth should reach Europa's surface every second. 
(Author's note: Much larger than I would have guessed!)

Besides those above, Osmanov uses two other results from the scientific 
literature: Bacteria that land on Europa's surface undergo 
"deactivation" in about 10,000 years, and about 20% to 40% of the moon's 
ice, which is 30 million to 80 million years old, undergoes fracturing 
from tidal heating and tidal friction from the titanic forces of Jupiter.

Simulations have found that regions of the ice can melt through in about 
1,000 years, carrying bacteria down to the ocean surface, with broader 
holes tens of kilometers wide occurring in about 10,000 years.

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What it could mean
Putting all these results together, Osmanov finds that "the total number 
of particles during the mentioned period is of the order of (3-8) x 
1023," or close to a mole of particles. This, he concludes, "strongly 
suggests the likelihood of life being present in the subsurface ocean of 
Europa if the biological and biochemical conditions are compatible with 
Earth-originating life, which would require a new series of 
investigations to determine."

We should be able to ascertain the presence of life on Europa when the 
European Space Agency's nuclear-powered Europa lander launches in 2027. 
Prototype drills tested in Antarctica were able to drill through 30 
kilometers (19 miles) of ice in 300 days, and, if successful, would be 
the first mission to directly access Europa's ocean and look for signs 
of life.

Written for you by our author David Appell, edited by Sadie Harley, and 
fact-checked and reviewed by Robert Egan—this article is the result of 
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Publication details
Zaza Osmanov, Earth as a potential source of life for Europa's 
subsurface ocean, International Journal of Astrobiology (2026). DOI: 
10.1017/s1473550426100354

Journal information: International Journal of Astrobiology

Key concepts
Interplanetary dustSpace probes
Who's behind this story?
David Appell
David Appell is an Oregon-based freelance science writer whose work has 
appeared in Scientific American, New Scientist, Physics World, and The 
Washington Post. He holds a Ph.D. in physics from Stony Brook 
University. Full profile →

Sadie Harley
BSc Life Sciences & Ecology. Microbiology lab background with 
pharmaceutical news experience in oil, gas, and renewable industries. 
Full profile →

Robert Egan
Bachelor's in mathematical biology, Master's in creative writing. 
Well-traveled with unique perspectives on science and language. Full 
profile →

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