Why scientists sent 600 black ants into space

A close look at the ant experiment onboard the International Space Station. (Credit: NASA)

An unmanned supply rocket delivered 600 small black common pavement ants to the International Space Station. Scientists want to see how they adjust to microgravity.

Analyzing how the ants adapt the innate algorithms that modulate their group behavior could help us understand how other groups, like searching robots, respond to difficult situations.

(Credit: João Vitor de Lacerda Gonzaga/Flickr)
(Credit: João Vitor de Lacerda Gonzaga/Flickr)

An ant colony monitors its environment—whether to identify a threat, find food, or map new terrain—by sending out worker ants to search the area. Because most ants have poor vision, and all ants rely on smell, an ant has to be close to something to detect it.

Further complicating matters, no single ant is in charge or coordinating the search. So how do they know how best to search?

Group dynamics

Ants communicate primarily by contacting each other by smell and touching antennae. Over millions of years, ants have developed algorithms that use the frequency with which these interactions occur to determine how many ants are in their area and, from that, how thoroughly they should conduct their search.


When antennae-to-antennae interactions occur frequently, the ants sense that the area is densely populated, and they circle around in small, random paths to gather robust information about their immediate area.

If the frequency of ant-to-ant interactions is low, however, the ants search in an entirely different manner. Instead of searching in small circles, they walk in straighter lines, giving up thoroughness in favor of covering more ground.

This technique is known as an expandable search network.

Ants aren’t the only animals to work out such algorithms. Humans have developed the same sort of protocols to govern how cellphone networks relay signals, or how a fleet of autonomous robots can search a building without the guidance of a central controller.

Like all networks, human-created networks have to deal with disruption. For example, if robots enter a burning building to assess damage or search for survivors, flames, smoke, and other elements could interfere with communications between the ‘bots and impede the search.

Adjusting to space

Scientists are developing workarounds for these situations, but Deborah Gordon, a biology professor at Stanford University who is leading the experiment, says that ants have already found solutions for conditions where information is not perfect.

In the space experiment, 70 ants were released into each of several small arenas roughly the size and shape of a tablet computer. The arena was divided into three sections, and video cameras tracked the ants’ searching patterns as the barriers were lowered, increasing the search area and thus decreasing the density of ants in the arena.

On Earth, Gordon says, ants adjust their search behavior as the arena expands by shifting from the small, circular search routine to straighter, broader paths, thus expanding the search network.

Performing the same experiment in microgravity is a way to introduce interference that is analogous to the radio disruption that robots might experience in a blazing building. In microgravity the ants struggle to walk, which in turn disrupts the ants’ ability to bump into each other and share information.

Observing how the space ants modified their search behavior when the loss of gravity interfered with their interactions, and their ability to assess density, could inform researchers how to design similar flexible protocols for robots and other devices that rely on expandable search networks.

“We have devised ways to organize the robots in a burning building, or how a cellphone network can respond to interference, but the ants have been evolving algorithms for doing this for 150 million years,” Gordon says. “Learning about the ants’ solutions might help us design network systems to solve similar problems.”

Source: Stanford University