The smell of rain, revisited: can tiny bubbles carry bacteria, too?

The starting point: what a smell is and how it travels are different questions

The earthy smell after rain. Knowing which substances produce it does not fully explain why it reaches your nose from the ground. Here we follow research on a mechanism that moves material from the soil surface into the air, rather than research identifying every component of the smell. Change the question from "What is it made of?" to "How does it move?" and a story about chemistry connects with the physics of fluids.

An editorial perspective This section offers comparisons and questions based on facts in the sources. It does not claim a shared underlying principle or present new research results.

2015: bubbles burst inside raindrops

An MIT research team used high-speed imaging to study raindrop-like water droplets striking wettable, porous surfaces. Under the right conditions, small air bubbles formed inside the droplets and burst, releasing even finer droplets. These became airborne aerosols. Large splashes were not the only route from the ground into the air: events inside a droplet could also carry material. The work suggested a possible way to transport substances responsible for smells, but it did not demonstrate the cause of every smell associated with rain.

2017: from "it could carry material" to experiments with bacteria

Follow-up work progressed to dropping water onto soil containing bacteria, collecting the ejected aerosols, and culturing them. The researchers found cases in which bacteria moved from the soil into droplets and survived for at least one hour after aerosol formation. The key advance is that the physical transport pathway observed in 2015 was joined in 2017 by a different piece of evidence: living bacteria could also be transferred. This study did not measure the probability of infection on rainy days.

A comparison: does rain wash particles out or send them into the air?

At first, these sound contradictory. But a raindrop collecting particles as it falls through the air and a droplet releasing tiny droplets when it strikes the ground occur in different places and at different stages. A separate MIT study investigated aerosol collection by falling droplets. "Rain cleans the air" and "rain releases particles" can both be valid explanations when their conditions are retained. One experiment alone cannot determine whether the overall amount increases or decreases.

The 2026 source check: what was established and what we have not followed up

For this article, we checked the 2015 mechanism study, the 2017 follow-up study involving bacteria, and the associated MIT announcements. The 2017 announcement also explains that results vary with soil type, temperature, impact speed, and other conditions. October 29, 2026 is this article's source verification date, not a claim that it covers all research through that date. This review does not establish how much long-distance transport occurs outdoors, what fraction of the total release comes from rain, or how later replication studies may have changed the estimates.

A perspective to take away: a discovery creates new experiments, not just answers

A single line such as "the mystery of rain's smell is solved" hides what was tested afterward. Filming a mechanism, measuring what it carries, and establishing its scale outdoors are three different tasks. Separating them reveals both progress and unresolved questions. When a science story catches your attention, try making separate notes for the observed phenomenon, the proposed explanation, and the effects in the real environment. This turns surprise into a question that can keep being tested.

An editorial perspective This section offers comparisons and questions based on facts in the sources. It does not claim a shared underlying principle or present new research results.