Mauna Kea is the only possible site for the controversial Thirty Meter Telescope, after an alternate site in the Canary Islands has reportedly been nixed.
According to Spanish news outlets, sources within Spain’s Ministry of Science, Innovation and Universities confirmed that the TMT International Observatory has rejected a bid by the Spanish government to have the long-planned telescope built on the island of La Palma in the Canary Islands.
The news comes little more than a month after TMT itself announced that Spain had proposed a “financial framework” to build the observatory on La Palma, a proposal involving multiple Spanish government agencies and the European Investment Bank. That proposed framework could have mobilized up to €1 billion (about $1.1 billion) for the project.
According to Spanish news site El Diario, the Ministry of Science, Innovation and Universities announced the rejection on Friday, but the reasons for that rejection were not publicly disclosed.
While Mauna Kea has always been the primary site planned for TMT, La Palma had been proposed as a potential alternative. The island hosts several telescopes at its Roque de los Muchachos Observatory, as its height and equatorial position makes it well-suited for astronomy in the same way that Mauna Kea is.
However, a 2024 evaluation of TMT by the National Science Foundation noted that the La Palma contingency was not developed to the same level of detail as the Mauna Kea plan.
With La Palma seemingly out of the picture, TMT’s only remaining potential site is, once again, Mauna Kea.
But the future of the project remains murky. In 2024, the NSF named both TMT and the Giant Magellan Telescope in Chile as potential linchpins of a “U.S. Extremely Large Telescope” project, but also that only one could feasibly be funded, putting the two telescopes in competition with each other.
In 2025, the NSF published a budget request that mentioned that it was no longer considering TMT for the Extremely Large Telescope project, wiping about $1.6 billion in federal funding off the table for TMT.
Nonetheless, Congress passed a bill earlier this year stipulating that NSF continue to consider both TMT and the Giant Magellan Telescope through its final review process, although no funding for either project was guaranteed in that bill.
Meanwhile, Gov. Josh Green and the state’s Congressional delegation have urged TMT to consider building the observatory in the footprint of a previously existing telescope on Mauna Kea, rather than on untouched summit land. TMT project manager Fengchuan Liu told the Mauna Kea Stewardship and Oversight Authority in April that this could be feasible.
Aloha State Daily has requested comment from TMT.
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