APOD: 2026 November 2 – A Long Cloud On Mars

NASA’s Astronomy Picture of the Day on Nov. 2, 2026, features a 2018 image of the Arsia Mons Elongated Cloud, a water-ice formation on Mars that can trail more than 1,500 kilometers downwind from the volcano. The daily feature describes when the cloud appears and outlines why its formation remains a puzzle for researchers studying the Martian atmosphere.

The cloud, commonly abbreviated AMEC, forms near Arsia Mons, a large Martian volcano, before winds carry it downstream into a long tail. NASA’s APOD account says the tail can extend over 1,500 kilometers. The image selected for the Nov. 2 feature was taken in 2018; the agency credits the European Space Agency, the German Aerospace Center and Freie Universität Berlin, with processing and licensing credited to J. Cowart.

AMEC is reported to appear during Mars’ spring and summer, and only in the morning hours. NASA identifies it as a water-ice cloud. The feature says the familiar Earth process in which ice crystals form around dust particles would not readily explain the cloud at its high-altitude location, where the Martian atmosphere is thin and dust is scarce.

The feature describes the idea that dust may not be involved as the leading speculation, not as a settled explanation. NASA says efforts to understand the cloud will continue. The APOD is an explanatory astronomy feature rather than an announcement of a new spacecraft observation or a newly reported research result.

A Clue to Martian Cloud Formation

AMEC matters because it offers researchers a visible example of cloud formation under atmospheric conditions quite different from those on Earth. Its seasonal and morning-only appearance, along with its great length, gives scientists a pattern to investigate. Understanding how water ice forms and spreads there could add to a broader understanding of cloud processes on Earth, as NASA’s feature notes.

The image also helps make clear that Martian weather is not limited to small, isolated clouds. A formation beginning near one volcano can be stretched by winds into a feature more than 1,500 kilometers long. That scale makes the cloud useful for examining how local terrain and atmospheric motion interact, although the APOD account does not claim that the image alone resolves those mechanisms.

Popular right now

Samsung 75-Inch M80H Series Mini LED 4K Smart TV (2026)

AmazonView Latest Price

De'Longhi Magnifica XS ECAM22110B Automatic Espresso Machine

AmazonView Latest Price

Roborock H60 Ultra-B Cordless Stick Vacuum Cleaner

AmazonView Latest Price

As an affiliate, we earn on qualifying purchases.

From Viking Orbiter to Mars Express

The cloud has been observed for decades. NASA says it was first recorded by Viking Orbiter 2 in 1977. More recent observations have captured it in greater detail through the European Space Agency’s robotic Mars Express spacecraft. The Nov. 2 APOD uses an image from 2018, placing the featured view within that longer history of observation.

NASA’s Astronomy Picture of the Day presents a different image or photograph of the universe each day, accompanied by an explanation written by a professional astronomer. The Nov. 2 entry is credited to authors and editors Robert Nemiroff, Jerry Bonnell, Cecilia Chirenti and Keighley Rockcliffe. Its purpose here is to explain an unusual Martian feature and the open questions about it, rather than to report a change in the cloud’s status on that date.

How the Ice Cloud Begins

The exact process that starts AMEC formation is not established in the APOD account. NASA says the usual dust-related explanation for cloud ice crystals would fail under the thin, dust-poor conditions described at the cloud’s altitude, and reports that leading speculation excludes dust. The feature does not identify a confirmed alternative process or give evidence that settles the question.

The APOD also does not provide new measurements, a detailed account of the 2018 observation, or a forecast for when the cloud will next appear. It describes recurring conditions—spring and summer, during morning hours—but does not specify the timing or extent of any particular future occurrence. Further research is needed to establish how the cloud forms and what controls its length.

Continued Study of AMEC

NASA says efforts to better understand the Arsia Mons Elongated Cloud will continue. The APOD does not announce a specific upcoming observation, mission milestone or research publication. Future observations and analysis will need to clarify how the cloud forms in a thin atmosphere, why it appears during particular seasons and morning hours, and how winds shape its long downstream tail.

For now, the Nov. 2 image and explanation add to a record that stretches from Viking Orbiter 2’s 1977 sighting to later observations by Mars Express. A clearer account of the cloud’s formation could help researchers compare atmospheric processes on Mars and Earth, but NASA’s feature leaves that scientific question open.

Key Questions

What is the long cloud on Mars?

It is the Arsia Mons Elongated Cloud, or AMEC, a water-ice cloud that forms near the Martian volcano Arsia Mons and is carried downwind.

How long can the cloud become?

NASA’s APOD says its downstream tail can extend over 1,500 kilometers. The feature does not say that every appearance reaches that length.

When does AMEC appear?

According to NASA’s feature, it forms during spring and summer and only during morning hours. The APOD does not give a forecast for a specific future appearance.

Do scientists know how the cloud forms?

No confirmed formation mechanism is given in the APOD. NASA says the standard dust-related process does not fit the described conditions, and that leading speculation holds dust is not involved.

Is the featured image a new observation?

No. The image featured on Nov. 2, 2026, dates to 2018. NASA says Viking Orbiter 2 first recorded the cloud in 1977 and that Mars Express has imaged it in greater detail more recently.

Source: science.nasa.gov